PURPOSE: To reduce the replacing time of a punch holder and to improve safety by attaching the punch holder only by lowering a press ram and detaching it by turning an operation handle.

CONSTITUTION: When a ram 1 is lowered after inserting the upper end of a shank 33 into a shank hole 2, a sliding piece 31 is pushed up by the upper surface 34a of a punch holder 34. With the rise of the sliding piece 31, the pressing surface presses the outer peripheral surface 33a of shank 33 by a wedge action to hold the shank 33 by a sufficient pressing force. A claw 16b of locking member 16 is engaged with an annular groove 33b of shank 33 by the intrusion of shank 33, to mount the punch holder 34 on the ram 1. When a handgrip 13 of operation handle is thrown down forward for detaching the holder 34 from the ram 1; the claw 16b of locking member 16 is drawn back and an eccentric cam 10 is turned at the same time, to move a carriage 25 forward thereby lowering the slide rest 31. Accordingly, the pressing force for the outer peripheral surface 33a of shank 33 is eliminated, and the punch holder 34 falls by its own weight.