diff --git a/src/types/request/v5-user.ts b/src/types/request/v5-user.ts
index 950f6fe..c8a3f5e 100644
--- a/src/types/request/v5-user.ts
+++ b/src/types/request/v5-user.ts
@@ -37,5 +37,5 @@ export interface UpdateSubApiKeyUpdateParamsV5 {
 }
 
 export interface DeleteSubMemberParamsV5 {
-  subMemberId: number;
+  subMemberId: string;
 }
diff --git a/test/v5/private.write.test.ts b/test/v5/private.write.test.ts
index c590c4d..ffbf324 100644
--- a/test/v5/private.write.test.ts
+++ b/test/v5/private.write.test.ts
@@ -412,7 +412,7 @@ describe('Private WRITE V5 REST API Endpoints', () => {
     it.skip('deleteSubMember()', async () => {
       expect(
         await api.deleteSubMember({
-          subMemberId: 1,
+          subMemberId: '1',
         }),
       ).toMatchObject({
         // ...successResponseObjectV3(),