diff --git a/dictation_server/src/common/token/typeguard.ts b/dictation_server/src/common/token/typeguard.ts
index d32ecad..04d3ddb 100644
--- a/dictation_server/src/common/token/typeguard.ts
+++ b/dictation_server/src/common/token/typeguard.ts
@@ -10,7 +10,6 @@ export const isIDToken = (
   if (token.emails === undefined) return false;
   if (token.exp === undefined) return false;
   if (token.iat === undefined) return false;
-  if (token.nonce === undefined) return false;
 
   return true;
 };
diff --git a/dictation_server/src/common/token/types.ts b/dictation_server/src/common/token/types.ts
index 059afc0..43650af 100644
--- a/dictation_server/src/common/token/types.ts
+++ b/dictation_server/src/common/token/types.ts
@@ -30,7 +30,7 @@ export type AccessToken = {
 
 export type IDToken = {
   emails: string[];
-  nonce: string;
+  nonce?: string | undefined;
   sub: string; // AzureAD B2C ID
   exp: number; // 有効期限
   iat: number; // 発行日時