'全体によく書けていますね！ v(^^*
Sub continue_works()
    Call sheet_delete
    Call print_form_amend
    Call get_number
    Call company_name_sort
    Call made_denpyo
End Sub
Sub sheet_delete()
    Dim ss As Worksheet
    Application.DisplayAlerts = False
    For Each ss In Worksheets
        If Left((ss.Name), 4) <> "main" Then
            ss.Delete
        End If
    Next
    Application.DisplayAlerts = True
End Sub
Sub get_number()
    Dim ctn As Long
    Dim lastrow As Long
    lastrow = Worksheets("main").Range("b65536").End(xlUp).Row
    For ctn = 2 To lastrow
        Worksheets("main").Range("a" & ctn).Value = ctn - 1
     Next
    Worksheets("main").Range("a1").Value = "No."
End Sub
Sub company_name_sort()
    Worksheets("main").Range("A1:G317").Sort _
    Key1:=Range("B2"), _
    Order1:=xlAscending, _
    Header:=xlYes
    Range("B1").Select
End Sub
Sub number_return_delete()
    Dim lastrow As Long
    lastrow = Worksheets("main").Range("b65536").End(xlUp).Row
'    Worksheets("main").Range("A1:G" & lastrow).Sort _
'    Key1:=Range("a1"), _
'    Order1:=xlAscending, _
'    Header:=xlYes
    '↓シート「main」がアクティブでないので、key1の指定がシート名から必要です。よくあるハマりです。そういう意味では、 company_name_sort の並べ替えも、たまたまうまく言っているだけです。
    Worksheets("main").Range("A1:G" & lastrow).Sort _
    Key1:=Worksheets("main").Range("a1"), _
    Order1:=xlAscending, _
    Header:=xlYes
    
    Columns("A:A").Delete
    Columns("a:a").Insert
    Columns("B:B").ColumnWidth = 10
    Columns("a:a").ColumnWidth = 5
End Sub
Private Sub Sort_by_Torihikisaki()
    Range("A1:G317").Sort _
        Key1:=Range("B1"), _
        Order1:=xlAscending, _
        Header:=xlYes
End Sub
Private Sub Sort_by_No()
    Range("A1:G317").Sort _
        Key1:=Range("A1"), _
        Order1:=xlAscending, _
        Header:=xlYes
End Sub

Sub made_denpyo()
    '↓以下のコメント、秀逸！ v(^^*
    '手順1）：main1シートをコピーする
    '手順2）：新シート名前を取得
    '手順3）：新シートのrangeB～RangeKまで内容転記
    '手順4）：ForNextを使って全ての取引先名でシート作成
    '手順5）：罫線作成
    Dim ctn As Long
    Dim into As Long
    Dim n As String
    Dim ss As Worksheet
    Dim st As Worksheet
    Set st = Worksheets("main")
    Dim lastrow As Long
    lastrow = Worksheets("main").Range("b65536").End(xlUp).Row
    For ctn = 2 To lastrow
    
        '↓If ... End If の間、インデントひとつ少ないです。
    If st.Range("b" & ctn).Value <> st.Range("b" & ctn - 1).Value Then
    '罫線作成タイミングは新規シート作成手前
        If ctn > 2 Then
            Call keisen
        End If
        Sheets("main1").Select
        Sheets("main1").Copy After:=Sheets(Sheets.Count)
        Set ss = ActiveSheet
        n = st.Range("b" & ctn).Value
        ss.Name = n
        into = 16
    End If
        ss.Range("e" & into).Value = st.Range("d" & ctn).Value
        ss.Range("f" & into).Value = st.Range("e" & ctn).Value
        ss.Range("h" & into).Value = st.Range("f" & ctn).Value
        If st.Range("g" & ctn).Value > 0 Then
            ss.Range("i" & into).Value = st.Range("g" & ctn).Value
        Else
            ss.Range("j" & into).Value = st.Range("g" & ctn).Value
        End If
            '↓インデントひとつ余計です。
            ss.Range("b" & into).Value = Right(Year(dt), 2)
            ss.Range("c" & into).Value = Month(dt)
            ss.Range("d" & into).Value = Day(dt)
            into = into + 1
    Next
    Call keisen
    Call number_return_delete
End Sub
Sub keisen()
    Dim lr As Long
    lr = Range("b65536").End(xlUp).Row
    
    'select, selectionがない状態にしたいですね。
    Range("B16:K" & lr + 1).Select
    Selection.Borders(xlDiagonalDown).LineStyle = xlNone
    Selection.Borders(xlDiagonalUp).LineStyle = xlNone
    With Selection.Borders(xlEdgeLeft)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeTop)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeBottom)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlEdgeRight)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlInsideVertical)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
    With Selection.Borders(xlInsideHorizontal)
        .LineStyle = xlContinuous
        .ColorIndex = 0
        .TintAndShade = 0
        .Weight = xlThin
    End With
End Sub
Sub print_form_amend()
    '以下の with ... endwith は、実は、シート「main1」の書式をいじれば不要でした (^^;
    With ActiveSheet.PageSetup
        .LeftHeader = "&A"
        .CenterHeader = ""
        .RightHeader = ""
        .LeftFooter = "&D"
        .CenterFooter = ""
        .RightFooter = ""
        .LeftMargin = Application.InchesToPoints(0.78740157480315)
        .RightMargin = Application.InchesToPoints(0.78740157480315)
        .TopMargin = Application.InchesToPoints(0.984251968503937)
        .BottomMargin = Application.InchesToPoints(0.984251968503937)
        .HeaderMargin = Application.InchesToPoints(0.511811023622047)
        .FooterMargin = Application.InchesToPoints(0.511811023622047)
    End With
    Application.PrintCommunication = True
    ActiveWindow.View = xlPageLayoutView
    ActiveWindow.View = xlPageBreakPreview
    ActiveSheet.PageSetup.PrintArea = "$A$1:$M$36"
End Sub