diff --git a/src/main/java/com/com/cnu/devlog_springboot/controller/PostController.java b/src/main/java/com/com/cnu/devlog_springboot/controller/PostController.java
index 7d6847f..1874a51 100644
--- a/src/main/java/com/com/cnu/devlog_springboot/controller/PostController.java
+++ b/src/main/java/com/com/cnu/devlog_springboot/controller/PostController.java
@@ -3,6 +3,8 @@
 import com.com.cnu.devlog_springboot.model.Post;
 import com.com.cnu.devlog_springboot.model.request.PostRequest;
 import com.com.cnu.devlog_springboot.service.PostService;
+import com.com.cnu.devlog_springboot.type.Tag;
+import jakarta.annotation.Nullable;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
@@ -17,8 +19,8 @@ public class PostController {
 
     // GET /posts
     @GetMapping
-    public ResponseEntity<List<Post>> getPosts() {
-        return ResponseEntity.ok(postService.getPosts());
+    public ResponseEntity<List<Post>> getPosts(@RequestParam("tag") @Nullable Tag tag{
+        return ResponseEntity.ok(postService.getPosts(tag));
     }
 
     // GET /posts/{postId}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/controller/ProjectController.java b/src/main/java/com/com/cnu/devlog_springboot/controller/ProjectController.java
new file mode 100644
index 0000000..5db88c2
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/controller/ProjectController.java
@@ -0,0 +1,54 @@
+package com.com.cnu.devlog_springboot.controller;
+
+import com.com.cnu.devlog_springboot.model.Project;
+import com.com.cnu.devlog_springboot.model.request.ProjectRequest;
+import com.com.cnu.devlog_springboot.service.ProjectService;
+import com.com.cnu.devlog_springboot.type.Tag;
+import jakarta.annotation.Nullable;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/projects")
+@RequiredArgsConstructor
+public class ProjectController {
+    private final ProjectService projectService;
+
+    // GET /projects
+    @GetMapping
+    public ResponseEntity<List<Project>> getProjects() {
+        return ResponseEntity.ok(projectService.getProjects());
+    }
+
+    // GET /projects/{projectId}
+    @GetMapping("{projectId}")
+    public ResponseEntity<Project> getProject(@PathVariable("projectId")Integer projectId) {
+        return ResponseEntity.ok(projectService.getProject(projectId));
+    }
+
+    // POST /projects
+    @PostMapping
+    public ResponseEntity<Project> createProject(@RequestBody ProjectRequest projectRequest) {
+        return ResponseEntity.ok(projectService.creatProject(projectRequest));
+    }
+
+    // PUT /projects/{projectId}
+    // ex. localhost:8080/projects/3
+    @PutMapping("{projectId}")
+    public ResponseEntity<Project> updateProject(
+            @PathVariable("projectId")Integer projectId,
+            @RequestBody ProjectRequest projectRequest
+    ) {
+        return ResponseEntity.ok(projectService.updateProject(projectId, projectRequest));
+    }
+
+    // DELETE /projects/{projectId}
+    @DeleteMapping("{projectId}")
+    public ResponseEntity<Void> deleteProject(@PathVariable("projectId") Integer projectId) {
+        projectService.deleteProject(projectId);
+        return ResponseEntity.noContent().build();
+    }
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/exception/DevlogException.java b/src/main/java/com/com/cnu/devlog_springboot/exception/DevlogException.java
new file mode 100644
index 0000000..9da0b4e
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/exception/DevlogException.java
@@ -0,0 +1,11 @@
+package com.com.cnu.devlog_springboot.exception;
+
+import com.com.cnu.devlog_springboot.type.ErrorCode;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class DevlogException extends RuntimeException {
+    private final ErrorCode errorCode;
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/exception/GlobalExceptionHandler.java b/src/main/java/com/com/cnu/devlog_springboot/exception/GlobalExceptionHandler.java
new file mode 100644
index 0000000..fe0fd60
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/exception/GlobalExceptionHandler.java
@@ -0,0 +1,26 @@
+package com.com.cnu.devlog_springboot.exception;
+
+import com.com.cnu.devlog_springboot.model.response.ErrorResponse;
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+
+@ControllerAdvice
+public class GlobalExceptionHandler {
+    @ExceptionHandler(DevlogException.class)
+    public ResponseEntity<ErrorResponse> handleDevlogException(
+            HttpServletRequest request, DevlogException e
+    ) {
+        return ResponseEntity.status(e.getErrorCode().getHttpStatus())
+                .body(
+                        new ErrorResponse(
+                                e.getErrorCode().getDescription(),
+                                e.getErrorCode().getHttpStatus().value(),
+                                e.getErrorCode().getErrorCode(),
+                                request.getRequestURI()
+                        )
+                );
+    }
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/model/response/ErrorResponse.java b/src/main/java/com/com/cnu/devlog_springboot/model/response/ErrorResponse.java
new file mode 100644
index 0000000..79353b3
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/model/response/ErrorResponse.java
@@ -0,0 +1,11 @@
+package com.com.cnu.devlog_springboot.model.response;
+
+public record ErrorResponse (
+        String title,
+        Integer status,
+        Integer code,
+        String instance
+
+) {
+
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/repository/PostRepository.java b/src/main/java/com/com/cnu/devlog_springboot/repository/PostRepository.java
index bb39395..21b7f8d 100644
--- a/src/main/java/com/com/cnu/devlog_springboot/repository/PostRepository.java
+++ b/src/main/java/com/com/cnu/devlog_springboot/repository/PostRepository.java
@@ -1,13 +1,17 @@
 package com.com.cnu.devlog_springboot.repository;
 
 import com.com.cnu.devlog_springboot.model.Post;
+import com.com.cnu.devlog_springboot.type.Tag;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+
 @Repository
 public interface PostRepository extends JpaRepository<Post, Integer> {
 //    Post save(Post post);
 //    List<Post> findAll();
 //    Optional<Post> findById(Integer postId);
 //    void delete(Post post);
+  List<Post> findAllByTag(Tag tag);
 }
diff --git a/src/main/java/com/com/cnu/devlog_springboot/repository/ProjectRepository.java b/src/main/java/com/com/cnu/devlog_springboot/repository/ProjectRepository.java
new file mode 100644
index 0000000..bb3f824
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/repository/ProjectRepository.java
@@ -0,0 +1,16 @@
+package com.com.cnu.devlog_springboot.repository;
+
+import com.com.cnu.devlog_springboot.model.Project;
+import com.com.cnu.devlog_springboot.type.Tag;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+
+@Repository
+public interface ProjectRepository extends JpaRepository<Project, Integer> {
+//    Project save(Project project);
+//    List<Project> findAll();
+//    Optional<Project> findById(Integer projectId);
+//    void delete(Project project);
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/service/PostService.java b/src/main/java/com/com/cnu/devlog_springboot/service/PostService.java
index 3823d7a..55c518e 100644
--- a/src/main/java/com/com/cnu/devlog_springboot/service/PostService.java
+++ b/src/main/java/com/com/cnu/devlog_springboot/service/PostService.java
@@ -1,8 +1,12 @@
 package com.com.cnu.devlog_springboot.service;
 
+import com.com.cnu.devlog_springboot.exception.DevlogException;
 import com.com.cnu.devlog_springboot.model.Post;
 import com.com.cnu.devlog_springboot.model.request.PostRequest;
 import com.com.cnu.devlog_springboot.repository.PostRepository;
+import com.com.cnu.devlog_springboot.type.ErrorCode;
+import com.com.cnu.devlog_springboot.type.Tag;
+import jakarta.annotation.Nullable;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 
@@ -13,7 +17,10 @@
 public class PostService {
     private final PostRepository postRepository;
 
-    public List<Post> getPosts() {
+    public List<Post> getPosts(@Nullable Tag tag) {
+        if (tag != null) {
+            return postRepository.findAllByTag(tag);
+        }
         return postRepository.findAll();
     }
 
@@ -38,7 +45,7 @@ public Post updatePost(Integer postId, PostRequest postRequest) {
 
     public Post getPost(Integer postId) {
         return postRepository.findById(postId)
-                .orElse(null);
+                .orElseThrow(() -> new DevlogException(ErrorCode.POST_NOT_FOUND));
     }
 
     public void deletePost(Integer postId) {
diff --git a/src/main/java/com/com/cnu/devlog_springboot/service/ProjectService.java b/src/main/java/com/com/cnu/devlog_springboot/service/ProjectService.java
new file mode 100644
index 0000000..f7ea528
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/service/ProjectService.java
@@ -0,0 +1,59 @@
+package com.com.cnu.devlog_springboot.service;
+
+import com.com.cnu.devlog_springboot.exception.DevlogException;
+import com.com.cnu.devlog_springboot.model.Project;
+import com.com.cnu.devlog_springboot.model.request.ProjectRequest;
+import com.com.cnu.devlog_springboot.repository.ProjectRepository;
+import com.com.cnu.devlog_springboot.type.ErrorCode;
+import com.com.cnu.devlog_springboot.type.Tag;
+import jakarta.annotation.Nullable;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+import java.time.LocalDate;
+import java.util.List;
+
+@Service
+@RequiredArgsConstructor
+public class ProjectService {
+    private final ProjectRepository projectRepository;
+
+    public List<Project> getProjects() {
+        return projectRepository.findAll();
+    }
+
+    public Project creatProject(ProjectRequest projectRequest) {
+        return projectRepository.save(new Project(
+                null,
+                projectRequest.title(),
+                projectRequest.summary(),
+                projectRequest.contents(),
+                projectRequest.startDate(),
+                projectRequest.endDate()
+        ));
+    }
+
+    public Project updateProject(Integer projectId, ProjectRequest projectRequest) {
+        return projectRepository.findById(projectId)
+                .map(project -> {
+                    project.setTitle(projectRequest.title());
+                    project.setSummary(projectRequest.summary());
+                    project.setContents(projectRequest.contents());
+                    project.setStartDate(projectRequest.startDate());
+                    project.setEndDate(projectRequest.endDate());
+                    return projectRepository.save(project);
+                })
+                .orElseThrow(() -> new DevlogException(ErrorCode.PROJECT_NOT_FOUND));
+    }
+
+    public Project getProject(Integer projectId) {
+        return projectRepository.findById(projectId)
+                .orElseThrow(() -> new DevlogException(ErrorCode.PROJECT_NOT_FOUND));
+    }
+
+    public void deleteProject(Integer projectId) {
+        Project project = projectRepository.findById(projectId)
+                .orElseThrow(() -> new DevlogException(ErrorCode.PROJECT_NOT_FOUND));
+        projectRepository.delete(project);
+    }
+}
diff --git a/src/main/java/com/com/cnu/devlog_springboot/type/ErrorCode.java b/src/main/java/com/com/cnu/devlog_springboot/type/ErrorCode.java
new file mode 100644
index 0000000..0e5b05a
--- /dev/null
+++ b/src/main/java/com/com/cnu/devlog_springboot/type/ErrorCode.java
@@ -0,0 +1,30 @@
+package com.com.cnu.devlog_springboot.type;
+
+import lombok.Getter;
+import org.springframework.http.HttpStatus;
+
+@Getter
+public enum ErrorCode {
+    //4XX
+    POST_NOT_FOUND(
+            HttpStatus.NOT_FOUND,
+            4000,
+            "해당 게시물을 찾을 수 없습니다."
+    ),
+
+    PROJECT_NOT_FOUND(
+            HttpStatus.NOT_FOUND,
+            404,
+                    "해당 프로젝트을 찾을 수 없습니다."
+    );
+
+    private final HttpStatus httpStatus;
+    private final Integer errorCode;
+    private final String description;
+    ErrorCode(HttpStatus httpStatus, Integer errorCode, String description) {
+        this.httpStatus = httpStatus;
+        this.errorCode = errorCode;
+        this.description = description;
+    }
+
+}