PURPOSE: To reduce the spring-back of a side wall part by fixing a manifold having many cylinders to a slide of a single action press, sending a signal by an electrical scale provided between a frame and a slide and controlling the up-and-down operation of the cylinder.

CONSTITUTION: By applying a specific signal, a solenoid changeover valve is set to a specific position, and by allowing a blank holder 6 to descend, a material is inserted and held by the blank holder 6. In a state that a slide 1 descends to a prescribed position, an electric scale 10 disconnects a first specific signal and applies a second signal. The solenoid changeover valve being in a specific position is moved to other position, and the blank holder 6 is released. Subsequently, the slide 1 further descends and the electric scale 10 disconnects the second signal, the solenoid changeover valve is changed to other position, and the blank holder 6 descends together with the slide 1. Thereafter, the blank holder 6 inserts and holds the outside peripheral edge of the side wall together with a die 8. Next, the slide 1 further descends and the electric scale 10 applies the second signal and changes a position of the solenoid changeover valve, the blank holder 6 is released, and spring-back of a side wall of a product can be reduced.