A motor control unit determines whether a rotor of an electric motor is in rotation or not after the motor control unit is started up but before an initial operation, based on an encoder count value after the start-up of the motor control unit. When the electric motor is stopped, the initial operation is carried out so as to learn a correction value of phase difference between the encoder count value and an actual current-supply phase. When the electric motor is still rotated due to its inertia, a motor-stop control is carried out before the initial operation in order to completely stop the rotation of the rotor. In the motor-stop control, electric power is supplied to windings of two phases at the same time.