When starting a brushless motor, if the stop position of the rotor is detected between time t1 and time t2, a start-up excitation pattern in accordance with the rotor stop position is input for an initial energization time Ts1. Afterward, when the energization is stopped, a plurality of signals SL1, SL2, SL3, SL4 are generated in sequence in excitation switch timing signals in accordance with the rotational position of the coasting rotor. From these signals SL1 to SL4, the rotor position is detected using the second and subsequent signals SL2 to SL4 and then the process shifts to ordinary energization switch control. In accordance with the present invention, it is possible to start up a motor in a short time with a simple method so as to obtain a large torque during start-up.