To carry out automatic operation by eliminating back pressure and oil hammer in accordance with all variations of ram speed and ram stroke.

In the hydraulic circuit 27 of a hydraulic cylinder 17 that drives a ram 19 disposed in a turret punch press, a pneumatic piston type accumulator 55 is arranged in the middle of a return duct line 53 from the hydraulic cylinder 17 to the tank 37. An electropneumatic regulator 67 that variably supplies an air pressure for actuating this piston type accumulator 55 and a controller 29 that controls by an electric signal by a ram stroke are also disposed. Thus, the automatic operation is made possible by eliminating back pressure and oil hammer, in accordance with all variations of ram speed and ram stroke.