PURPOSE: To execute the prescribed punching by mounting each punch holder free to change an inner punch assembly on one by a pair of robot arms or a both sides driving type actuator and mounting a die to the other respectively.

CONSTITUTION: A punch holder 1PH1 consisting of a disk part 1 of top part and a center vertical direction shaft 2 of lower part is mounted on a robot arm H. A punch holder 2PH2 has an inner diameter part 8 to fit the center shaft part 2 in the center of a flange part 7 of top part free to slide in axial direction. Under this constitution, because a strippers S is sliding-guided precisely/surely in axial direction at the upper part of the punch holder 2PH2, is transferred while executing a punch stroke S1 by the motion of the robot arm and since there is no a punch retainer, etc., to slide on the outer diameter part of the stripper S, any risk to interface therewith is avoided, even through a formed part Wa already worked, etc., are existed near a point to be worked of the work W.