To continuously set the delay and advance of a phase to a prescribed value or less by decreasing acceleration in an acceleration range, where acceleration torque can be used largely, and by increasing the acceleration with respect to a range where acceleration torque can be used largely, within the acceleration range with the small acceleration torque.

The torque characteristics of a motor include the maximum self-activation frequency fs 507 of a pulse motor, a drive target frequency f2 508 of the pulse motor, acceleration torque Ta1 509 where the pulse motor can be used at a self-activation frequency f1, and acceleration torque Ta2 510 where the pulse motor can be used at a drive target frequency f2. Pull-out torque 501 of the general pulse motor is decreased, as a motor drive frequency (f) decreases. As a result, torque that is obtained by subtracting friction torque T1 503 and a torque margin 504 from the pull-out torque 501 becomes torque Ta that can be used for accelerating the pulse motor, so that the acceleration torque also becomes smaller, as the drive speed of the motor increases.