A motor driving part has half bridge circuits in which a high potential side drive transistor and a low potential side drive transistor are connected in series to each other, and a connection point therebetween serves as a stator winding driving terminal of each phase of a motor. A rotor position detector detects a rotor position of the motor and outputs a rotor position signal. The current phase detector detects the phase of a phase current flowing in the stator winding driving terminal. A voltage signal generator controls and generates a voltage profile signal such that a first phase difference that is a difference between the phase of the phase current and the phase of the rotor position signal is kept to a predetermined electrical angle. A driving signal generator generates a PWM signal that drives the drive transistor of each phase depending on the voltage profile signal.