To make a control valve controlling working liquid unnecessary by connecting a two-way operation type hydraulic actuator and a two-way discharge type hydraulic pump without mounting a valve to form a closed circuit, moving a movable member performing the plastic working of a material to be worked by the hydraulic actuator, detecting the moving amount of the actuator, and rotating a hydraulic pump by a motor whose rotation is controlled by the electric signal of the moving amount.

A hydraulic cylinder 2 is operated to bend a metal plate 14 by punch 4 and die 6. A position command signal D; is inputted to an electricity- hydraulic control system 8 by a system controller 9. The rotation direction, the rotation speed, and the rotation torque of a DC servomotor 11 are controlled by the system 8. By the rotation of the DC servomotor 11, a ram 3 existing on the lower part of the cylinder 2, is moved in a prescribed moving direction, at a moving speed, and by a moving force to work the metal plate 14. The position of the ram 3 is detected by a linear scale 7, a feedback signal Df is transmitted, and a position error is corrected.