diff --git a/vba_code_kukan_detail_master.txt b/vba_code_kukan_detail_master.txt
index 8a6ac79..9fd6105 100644
--- a/vba_code_kukan_detail_master.txt
+++ b/vba_code_kukan_detail_master.txt
@@ -414,12 +414,21 @@ Sub ExportMasterDetailData()
         csvContent = Left(csvContent, Len(csvContent) - 1)
     Loop
     
-    ' Write file
+    ' Write header using native VBA (no charset conversion)
+    Dim f As Long
+    f = FreeFile
+    Open savePath For Output As #f
+    Print #f, CSV_HEADER;
+    Close #f
+    
+    ' Append data using ADODB.Stream with shift_jis
     Dim stream As Object
     Set stream = CreateObject("ADODB.Stream")
     stream.Type = 2
     stream.Charset = "shift_jis"
     stream.Open
+    stream.LoadFromFile savePath
+    stream.Position = stream.Size
     stream.WriteText csvContent, 1
     stream.SaveToFile savePath, 2
     stream.Close