To conduct a synchronous position control of suspensions which are driven by a plurality of variable speed motors respectively.

The positions of suspensions which are provided with respective variable speed motors are detected by position detectors 11-1N. The outputs of the position detectors 11-1N are given to present position calculating sections 21-2N to calculate the present positions of the suspensions. When a synchronous position operation command signal is detected by an operation command input detector 4, the positions of the suspensions calculated by the present position calculating sections 21-2N are stored as operation start positions. Then, the movement amounts of the suspensions are calculated from the present positions and the operation start positions of the suspensions by movement amount calculating sections 61-6N respectively. The maximum values and the minimum values of the movement amounts are detected by a movement amount maximum value and minimum value detector 7 for one suspension after another and an average movement amount is calculated by a movement amount average calculating section 8. Deviations of the movement amounts of the suspensions from the average value and calculated by deviation calculating sections 91-9N respectively. Then, a correction amount to a speed standard is calculated based on the deviations and then is given to a feedback control system of each of the speed variable motors.