PURPOSE: To enable the rod position of a stepping cylinder which follows positional command to be controlled by analog operation with no possibility of step-out or no restriction in pulse motor speed.

CONSTITUTION: A time required for pulse trains to be outputted from a speed judger 22 through a V/F converter 23 is determined by a comparing operational circuit 26: when a pulse interruption time obtained by its subtraction from a control cycle approximates to the resonance cycle of a pulse motor for driving a stepping cylinder, an inversion circuit 25 is operated by operation command from the comparing operational circuit 26, thereby inverting the rotation direction command outputted from a forward/reverse judger 21 to a pulse motor drive circuit 80.