To simplify a circuit (hardware) required in the light of feedback control over a current value flowing into the solenoid of a solenoid valve.

A central processing unit 54 controls the current value of a solenoid valve installed in a hydraulic circuit of a forklift truck. In this case, a pulse width modulation signal conformed to the duty output value commanded by this CPU 54 is outputted from a pulse width modulation port 59. A transistor 60 connected in space between a battery and a solenoid 25a exercises its on-off operation on the basis of the pulse width modulation signal. The current flowed into the solenoid 25a is detected by a current detection circuit 52, and a detection signal (current detected value) S2 passed through a low-pass filter 53 is inputted into an analog-to-digital port 62. The CPU 54 executes current value controlling program data in succession, comparing the current detected value with the prestored desired current value, and thus it is made so as to compensate the duty output value so as to have both the values accorded with each other within the allowable range.