Windings of each phase in a three-phase AC motor are independent of one another. A motor control unit gives, to windings of each phase (U, V and W-phase), currents (IU, IV, IW) obtained by adding, to a fundamental sine wave current, a current having a frequency which is three times as high as that of the fundamental sine wave current. That is, IU=I·sin ωt+Ia·sin 3ωt: IV=I·sin (ωt+⅔π)+Ia·sin 3ωt: IW=I·sin (ωt+{fraction (4/3)}π)+Ia·sin 3ωt Also, amplitude Ia of a current having a frequency which is three times as high as that of the fundamental sine wave current is set to a predetermined value smaller than amplitude I of the fundamental sine wave current.