diff --git a/ThScoreFileConverter/Helpers/IntegerHelper.cs b/ThScoreFileConverter/Helpers/IntegerHelper.cs
index 3e8386ab..7011aade 100644
--- a/ThScoreFileConverter/Helpers/IntegerHelper.cs
+++ b/ThScoreFileConverter/Helpers/IntegerHelper.cs
@@ -6,7 +6,6 @@
 //-----------------------------------------------------------------------
 
 using System;
-using System.Globalization;
 using CommunityToolkit.Diagnostics;
 
 namespace ThScoreFileConverter.Helpers;