To improve the efficiency in punching work by determining a region of the interference of a head part of a reference pin and a pressure foot.

A cavity part 20 is formed on a lower part of a groove 12 of a table 7 of a printed board punching machine, and a holder 22 is fixed on its bottom to movably mount a proximity sensor 23. After a printed board 9 is placed on a table 7 in a state that one of reference pins 8 is engaged with a hole 11 and the other reference pin is engaged with a groove 12, a holder 22 is moved left, a motor 26 is immediately stopped when the proximity sensor 23 is switched on, and a moving distance of the holder 22 from a standby position is determined. Then a central coordinate of the other reference pin 8 positioned in the groove 12 is determined, and a region where the head part of the other reference pin and a pressing member are interfered with each other is determined. In a case when a tool moving path is contacted with the region or intersects the region in the movement of a tool, a height from a surface 9a is changed. The efficiency in punching work can be improved by minimizing the pulling-up amount of a pressure foot.