PURPOSE: To improve a starting probability by successively executing deexcitation drive action in each phase of a stator coil at the time of a stepping process, and ending the stepping process when a rotary member leads to a prescribed rotational speed.

CONSTITUTION: When a start signal is received by a control circuit 22b, an excitation counter 22f and a stepping timer 22g are set, to also set a number of repetition times (n) for supplying an excitation current at starting time, and the excitation current is supplied to coils (u), (v), (w). Here is performed deexcitation drive action in each phase not containing a successive stop period but reversing a direction from a negative to a positive of the excitation current. In the case that a motor 20 leads to a prescribed rotational speed, ordinary bipolar driving is performed thereafter transferred to acceleration driving. In the case of the motor 20 not reaching the prescribed rotational speed, a value 1 is added to a number of the repetition times (n), to again perform the deexcitation drive action. As a result, a change width of magnetic flux of a stator core 30 is increased to improve a starting probability of the motor 20.