PURPOSE: To provide a high-speed, low-vibration, low-noise and low-cost motor driving method.

CONSTITUTION: At every timing that is determined by a timer mechanism 9, a pulse duty ratio is set through a pulse-width modulation unit 2 on the basis of duty-ratio data. Consequently, a pulse duty-ratio in one step driven by a stepping motor 4 is changeable so that the motor power control is performed in an open loop.