To properly and gently start and stop a motor despite very simple overall constitution by combining an off-delay circuit, a ramp circuit, a duty ratio-variable circuit, and a switching element.

A ramp circuit 15 smoothly increases output voltage with respect to time and a duty ratio-variable circuit 16 sends to a switching element 18 pulse train signals with their duty ratio continuously increased according to the output voltage of the ramp circuit 15. The switching element 18 controls the interruption and passage of energizing current Im to a motor M according to the duty ratio of the pulse train signals and thereby gently starts the motor M. To stop the motor M, a closed forward start switch SW1 or reverse start switch SW2 is opened. At this time the ramp circuit 15 smoothly reduces the output voltage with respect to time, and the duty ratio of the energizing current Im is reduced with time through the duty ratio-variable circuit 16 and the switching element 18. As a result, the motor M is smoothly stopped.