PURPOSE: To improve the accuracy of speed control for a hydraulic actuator, reduce shock at braking time, lower the lowest value of driving force, and simplify the structure of a device.

CONSTITUTION: Discharge ports of two variable displacement pumps 11, 12 are respectively communicated to a pair of hydraulic fluid supply/discharge ports A, B of a hydraulic pressure actuator 10, and those discharge pressures are respectively controlled by pressure control devices 21, 22 in proportion to electric command signals. Displacement speed or displacement of the output axis 10c of the hydraulic actuator 10 is measured by a potentiometer 31, and electric signals are outputted from hydraulic actuator control devices 21, 22 so that a displacement speed or displacement command value may match its measured value, then its output is inputted, to a pressure control device as an electric command signal for showing manipulated variable.