A method for carrying out a boosting operation includes detecting that a boosting operation has been carried out for making a current value of an electric motor larger than a normal full open throttle value, detecting that an electric motor has not rotated, detecting that a predetermined time period has elapsed since the detection that the electric motor has not rotated; and after the detection that the predetermined time period has elapsed, controlling the current value of the electric motor to be equal to or smaller than a limit value that is smaller than the normal full open throttle value.