diff --git a/src/main/java/com/example/blism/domain/Mailbox.java b/src/main/java/com/example/blism/domain/Mailbox.java
index db290df..a8f1123 100644
--- a/src/main/java/com/example/blism/domain/Mailbox.java
+++ b/src/main/java/com/example/blism/domain/Mailbox.java
@@ -38,6 +38,7 @@ public class Mailbox extends BaseTimeEntity {
     @Builder
     private Mailbox(Member owner) {
         this.owner = owner;
+        this.visibility = 1;
     }
 
     public static Mailbox createMailbox(Member owner) {
diff --git a/src/main/java/com/example/blism/service/MemberServiceImpl.java b/src/main/java/com/example/blism/service/MemberServiceImpl.java
index 1197c8a..60f3377 100644
--- a/src/main/java/com/example/blism/service/MemberServiceImpl.java
+++ b/src/main/java/com/example/blism/service/MemberServiceImpl.java
@@ -31,9 +31,7 @@ public Long joinMember(MemberRequestDTO.signupDTO request) {
                 .nickname(request.getNickname())
                 .build();
 
-        Mailbox newMailbox = Mailbox.builder()
-                .owner(newMember)
-                .build();
+        Mailbox newMailbox = Mailbox.createMailbox(newMember);
 
         memberRepository.save(newMember);
         mailboxRepository.save(newMailbox);