PURPOSE: To stop a motor quickly and smoothly without causing reverse rotation by conducting the motor coil reversely and fixing the conducting direction when the r.p.m. of motor decreases to a predetermined value.

CONSTITUTION: A switch circuit 26 is connected with the bases of transistors 14, 18, 22, 24 in order to switch the direction of a motor coil 10 depending on the rotor position. A rotation detecting circuit 72 is provided with a comparator and a detection signal is fed to the switch circuit 26 when the upper voltage of a capacitor 74 exceeds a predetermined level. The switch circuit 26 stops the switch operation in response to the detection signal. In other words, the current flowing through the motor coil 10 is fixed to one direction. Consequently, the rotor of a single-phase motor is pulled to a position corresponding to one pattern of field and the motor is locked, i.e., stopped, under that state.