PURPOSE: To provide hold-down pieces capable of holding down a printed wiring board near the bank of a machining hole even when using a tool small in diameter and which can choose each hold-down piece automatically.

CONSTITUTION: A printed wiring board 6 mounted on a table 10 is fitted to a printed wiring board finishing device which machines the board 6 with a tool 2 held by a spindle 1. A hold-down member 13A is fitted in the direction in which the tool 2 travels, and has a through hole 13B through which the tool 2 with a maximum diameter can pass. On the under surface of the member 13A, a sliding groove 13C is formed at right angles to the axial direction of the spindle 1. A slide member 7A sliding along the sliding groove 13C and a sliding structure 8 sliding the member 7A are installed, and a plurality of hold-down pieces 7B, 7C different in hole diameter from the member 7A are fixedly installed in an unillustrated control device which chooses the hold-down piece 7B or 7C responding to a tool exchange command.