diff --git a/src/main/java/io/company/localhost/service/localbordService.java b/src/main/java/io/company/localhost/service/localbordService.java
index a06495d..71e4b77 100644
--- a/src/main/java/io/company/localhost/service/localbordService.java
+++ b/src/main/java/io/company/localhost/service/localbordService.java
@@ -23,6 +23,7 @@ import lombok.RequiredArgsConstructor;
 @RequiredArgsConstructor
 public class localbordService {
     private final localbordMapper boardMapper;
+    private static final long MAX_FILE_SIZE = 5 * 1024 * 1024; // 5MB
 
     public List<MapDto> getNotices(MapDto map) {
         List<MapDto> posts = boardMapper.getNotices(map);
@@ -55,13 +56,28 @@ public class localbordService {
         boardMapper.createBoard(map);
         return (BigInteger) map.get("LOCBRDSEQ");
     }
+    
+    public void addAttachment(MapDto map) {   
+        String boardSeqStr = (String) map.get("CMNBRDSEQ");
+        Long boardSeq = Long.parseLong(boardSeqStr);
+        map.put("CMNBRDSEQ", boardSeq);
+
+        String newFilename = UUID.randomUUID().toString();
+        map.put("CMNFLENAM", newFilename);
 
-    public void addAttachment(MapDto map) {
-    	String newFilename = UUID.randomUUID().toString();
-    	map.put("CMNFLENAM", newFilename);
         boardMapper.addAttachment(map);
     }
 
+    public void validateAttachmentsSize(List<MapDto> attachments) {
+        long totalSize = attachments.stream()
+            .mapToLong(attachment -> (Long) attachment.get("size"))
+            .sum();
+
+        if (totalSize > MAX_FILE_SIZE) {
+            throw new IllegalArgumentException("첨부파일의 총 용량이 5MB를 초과합니다.");
+        }
+    }
+
     public MapDto getBoardDetail(Long boardId) {
     	incrementViewCount(boardId);
         MapDto boardDetail = boardMapper.selectBoardDetail(boardId);