diff --git a/src/main/java/aromanticcat/umcproject/controller/NangmanLetterController.java b/src/main/java/aromanticcat/umcproject/controller/NangmanLetterController.java
new file mode 100644
index 0000000..9224798
--- /dev/null
+++ b/src/main/java/aromanticcat/umcproject/controller/NangmanLetterController.java
@@ -0,0 +1,36 @@
+package aromanticcat.umcproject.controller;
+
+import aromanticcat.umcproject.apiPayload.ApiResponse;
+import aromanticcat.umcproject.dto.NangmanLetterDTO;
+import aromanticcat.umcproject.service.NangmanLetterService;
+import io.swagger.annotations.ApiOperation;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/nangman-post")
+@RequiredArgsConstructor
+public class NangmanLetterController {
+
+    private final NangmanLetterService nangmanLetterService;
+
+    @PostMapping("/send")
+    @ApiOperation(value = "낭만 우편함 편지 등록")
+    public ApiResponse<NangmanLetterDTO> send(@RequestBody NangmanLetterDTO nangmanLetterDTO){
+        try{
+            //낭만 우편함 편지 작성 및 응답 DTO 변환
+            NangmanLetterDTO responseDTO  = nangmanLetterService.register(nangmanLetterDTO);
+
+            //전송 성공 응답 반환
+            return ApiResponse.onSuccess(responseDTO);
+
+        }catch (Exception e){
+            //에러 발생 시 실패 응답 반환
+            return ApiResponse.onFailure(HttpStatus.INTERNAL_SERVER_ERROR.toString(), e.getMessage(), null);
+        }
+    }
+}
diff --git a/src/main/java/aromanticcat/umcproject/dto/NangmanLetterDTO.java b/src/main/java/aromanticcat/umcproject/dto/NangmanLetterDTO.java
index 790adc5..a161783 100644
--- a/src/main/java/aromanticcat/umcproject/dto/NangmanLetterDTO.java
+++ b/src/main/java/aromanticcat/umcproject/dto/NangmanLetterDTO.java
@@ -1,6 +1,5 @@
 package aromanticcat.umcproject.dto;
 
-import aromanticcat.umcproject.entity.Member;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
@@ -14,6 +13,7 @@
 @NoArgsConstructor
 public class NangmanLetterDTO {
 
+    @NotNull
     private Long id;
 
     @NotNull(message = "sender_nickname은 null일 수 없습니다.")
@@ -41,6 +41,5 @@ public class NangmanLetterDTO {
     private Integer star_cnt;
 
     @NotNull(message = "member는 null일 수 없습니다.")
-    private Member member;
-
+    private Long member_id;
 }
diff --git a/src/main/java/aromanticcat/umcproject/service/NangmanLetterService.java b/src/main/java/aromanticcat/umcproject/service/NangmanLetterService.java
index 8c4c168..84e2df0 100644
--- a/src/main/java/aromanticcat/umcproject/service/NangmanLetterService.java
+++ b/src/main/java/aromanticcat/umcproject/service/NangmanLetterService.java
@@ -4,9 +4,9 @@
 
 public interface NangmanLetterService {
 
-    Long register(NangmanLetterDTO nangmanLetterDTO);
+    NangmanLetterDTO register(NangmanLetterDTO nangmanLetterDTO);
 
     NangmanLetterDTO readOne(Long id);
 
-    void modify(NangmanLetterDTO nangmanLetterDTO);
+    void receivedReply(NangmanLetterDTO nangmanLetterDTO);
 }
diff --git a/src/main/java/aromanticcat/umcproject/service/NangmanLetterServiceImpl.java b/src/main/java/aromanticcat/umcproject/service/NangmanLetterServiceImpl.java
index 4e6a4f9..6dd28c0 100644
--- a/src/main/java/aromanticcat/umcproject/service/NangmanLetterServiceImpl.java
+++ b/src/main/java/aromanticcat/umcproject/service/NangmanLetterServiceImpl.java
@@ -22,21 +22,23 @@ public class NangmanLetterServiceImpl implements NangmanLetterService{
     private final RandomNicknameService randomNicknameService;
 
     @Override
-    public Long register(NangmanLetterDTO nangmanLetterDTO){
+    public NangmanLetterDTO register(NangmanLetterDTO nangmanLetterDTO){
 
-        //랜덤 닉네임 생성
+        // 랜덤 닉네임 생성
         String randomNickname = randomNicknameService.generateRandomNickname();
 
-        //DTO에 랜덤 닉네임 설정
+        // DTO에 랜덤 닉네임 설정
         nangmanLetterDTO.setSender_nickname(randomNickname);
 
-        //DTO를 엔티티로 변환
+        // DTO를 엔티티로 변환
         NangmanLetter nangmanLetter = modelMapper.map(nangmanLetterDTO, NangmanLetter.class);
 
-        //엔티티 저장
+        // 엔티티 저장
         Long id = nangmanLetterRepository.save(nangmanLetter).getId();
 
-        return id;
+        nangmanLetterDTO.setId(id);
+
+        return nangmanLetterDTO;
     }
 
     @Override
@@ -51,15 +53,27 @@ public NangmanLetterDTO readOne(Long id){
         return nangmanLetterDTO;
     }
 
+
+
     //답장 받을 때 has_response 업데이트
     @Override
-    public void modify(NangmanLetterDTO nangmanLetterDTO) {
+    public void receivedReply(NangmanLetterDTO nangmanLetterDTO) {
         Optional<NangmanLetter> result = nangmanLetterRepository.findById(nangmanLetterDTO.getId());
 
         NangmanLetter nangmanLetter = result.orElseThrow();
 
+        //has_response 값 업데이트
         nangmanLetter.change(nangmanLetterDTO.getHas_response());
 
+        //is_public 값에 따라 낭만 모음집에 추가
+        if(nangmanLetter.getIs_public()){
+            addLetterToNangmanCollectoin(nangmanLetter);
+        }
         nangmanLetterRepository.save(nangmanLetter);
     }
+
+    private void addLetterToNangmanCollectoin(NangmanLetter nangmanLetter){
+        // 낭만 모음집에 해당 편지를 추가하는 로직을 구현
+        // 추가되는 방법은 해당 모음집의 컬렉션에 편지를 추가하거나 다른 적절한 방법으로 구현
+    }
 }
diff --git a/src/test/java/aromanticcat/umcproject/service/NangmanLetterServiceTests.java b/src/test/java/aromanticcat/umcproject/service/NangmanLetterServiceTests.java
index 5da3c47..fa86d31 100644
--- a/src/test/java/aromanticcat/umcproject/service/NangmanLetterServiceTests.java
+++ b/src/test/java/aromanticcat/umcproject/service/NangmanLetterServiceTests.java
@@ -1,9 +1,6 @@
 package aromanticcat.umcproject.service;
 
-import aromanticcat.umcproject.dto.NangmanLetterDTO;
-import aromanticcat.umcproject.entity.Member;
 import aromanticcat.umcproject.repository.MemberRepository;
-import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
 
@@ -19,38 +16,38 @@ public class NangmanLetterServiceTests {
     @Autowired
     private RandomNicknameService randomNicknameService;
 
-    @Test
-    public void testRegister(){
-        System.out.println(nangmanLetterService.getClass().getName());
-
-        Member member1 = memberRepository.findById(1L).orElseThrow(() -> new RuntimeException("Member not found"));
-
-        //랜덤 닉네임 생성
-        String randomNickname = randomNicknameService.generateRandomNickname();
-
-        NangmanLetterDTO nangmanLetterDTO = NangmanLetterDTO.builder()
-                .content("낭만 편지 샘플3")
-                .is_public(false)
-                .member(member1)
-                .build();
-
-        //생성된 랜덤 닉네임 설정
-        nangmanLetterDTO.setSender_nickname(randomNickname);
-
-        Long id = nangmanLetterService.register(nangmanLetterDTO);
-
-        System.out.println("id: " + id);
-    }
-
-    @Test
-    public void testModify(){
-
-        //변경에 필요한 데이터만
-        NangmanLetterDTO nangmanLetterDTO = NangmanLetterDTO.builder()
-                .id(4L)
-                .has_response(true)
-                .build();
-
-        nangmanLetterService.modify(nangmanLetterDTO);
-    }
+//    @Test
+//    public void testRegister(){
+//        System.out.println(nangmanLetterService.getClass().getName());
+//
+//        Member member1 = memberRepository.findById(1L).orElseThrow(() -> new RuntimeException("Member not found"));
+//
+//        //랜덤 닉네임 생성
+//        String randomNickname = randomNicknameService.generateRandomNickname();
+//
+//        NangmanLetterDTO nangmanLetterDTO = NangmanLetterDTO.builder()
+//                .content("낭만 편지 샘플3")
+//                .is_public(false)
+//                .member(member1)
+//                .build();
+//
+//        //생성된 랜덤 닉네임 설정
+//        nangmanLetterDTO.setSender_nickname(randomNickname);
+//
+//        Long id = nangmanLetterService.register(nangmanLetterDTO);
+//
+//        System.out.println("id: " + id);
+//    }
+
+//    @Test
+//    public void testModify(){
+//
+//        //변경에 필요한 데이터만
+//        NangmanLetterDTO nangmanLetterDTO = NangmanLetterDTO.builder()
+//                .id(4L)
+//                .has_response(true)
+//                .build();
+//
+//        nangmanLetterService.modify(nangmanLetterDTO);
+//    }
 }