Abstract: A fixing member (B, N) pierces a screw hole (13b) of a first clamping member (13) and an insertion hole (14c) of a second clamping member (14), and fixes the first and second clamping members (13, 14) to a workbench (12). The position of a workpiece (W) relative to the workbench is determined by utilizing the first and second clamping members (13, 14) fixed to the workbench (12) by the fixing member (B, N). The workpiece (W) moved to a space between a clamping face (13d) of the first clamping member (13) and a flange portion (14b) of the second clamping member (14) is fixed by a fastening member (15).