PURPOSE: To shorten a start-up time by supplying driving current to each stator phase winding by an initial phase driving signal, monitoring AC induced voltage as well and releasing an initial driving operation in case of starting of a motor.

CONSTITUTION: A three phase brushless motor is equipped with the stator phase windings 1(a)∼1(c) for driving, and its driving circuit is detected by the transistors 2(a)∼2(f), a change-over switch 3, a phase starting pulse circuit 4, a starting detection circuit 5, a three phase logic circuit 6, a stop detection circuit 7, etc. And, in case of driving of a motor, an initial phase driving signal is supplied to a stator phase winding driving circuit, and the driving current is supplied to each stator phase windings 1(a)∼1(c) thereby, and a rotor starts to rotate. AC induced voltage is brought on the stator phase windings 1(a)∼1(c) by rotation of the rotor, and its amplitude is discriminated. When it is in excess of a specific value, it is switched from the initial phase driving signal to a phase driving signal, a continuity angle of the driving current supplied to the said windings 1(a)∼1(c) is set by AC induced voltage and the motor is rotated stably.