To avoid a stepped out brushless motor caused by counter-electromotive force by providing a changeover control part which changes compulsory synchronous control over to feedback synchronous control, when the phase difference between a compulsory synchronous control signal and a feedback synchronous control signal becomes a specified value or less.

A feedback synchronous control signal generating part 130 generates feedback synchronous control signals VU1, VV1, VW1 for performing changeover of driving currents which are caused to flow in stator windings by a driving circuit, on the basis of a zero-cross point. Next, a changeover control part 135 changes control of a brushless motor from compulsory synchronous control over to feedback synchronous control, when the phase difference between compulsory synchronous control signals VU2, VV2 VW2 and the feedback synchronous control signals VU1, VV1, VW1 becomes a specified value or less. A driving voltage changeover part 136 starts the brushless motor by a driving voltage lower than a rated driving voltage. After the control is changed over to feedback synchronous control, the driving voltage is changed over to the rated driving voltage. Consequently, increase of the driving current and step out of the brushless motor which used to occur on the occasion of changeover are prevented.