A1にまとめる

Sub A1にまとめる()

Dim mySheet As String
Dim i, j As Long
Dim sheetsCount As Long
Dim lastRow As Long
Dim output As String


Application.ScreenUpdating = False 'マクロを実行中、画面更新を中断
ActiveSheet.EnableCalculation = False    '---再計算しない
'Application.ScreenUpdating = True '画面更新
'ActiveSheet.EnableCalculation = True     '---再計算する

i = 0
j = 0
lastRow = 0
output = ""

mySheet = ActiveSheet.Name 'シート名を取得
sheetsCount = ActiveWorkbook.Worksheets.Count 'シートの数を取得

For i = 1 To sheetsCount
    Worksheets(i).Select 'シートの選択
    lastRow = Cells(60000, 1).End(xlUp).Row  '最終行を取得
    
    For j = 1 To lastRow
        If j <> 1 Then 'A1は除外
        output = output & Cells(j, 1)  '2〜最終行の文字列を足す
        End If
    Next
Next

Cells.WrapText = False '折り返しを無くす

Worksheets(mySheet).Activate  'マクロ開始のシートを選択
Cells(1, 1).Select  'A1を選択

Application.ScreenUpdating = True '画面更新
ActiveSheet.EnableCalculation = True     '---再計算する

End Sub