Provided is an AC motor in a three-phase unbalanced state such as a claw-teeth type AC motor (108), which is reduced in magnetic flux pulsations and torque pulsations. Among the current command values of individual phases to be intrinsically given to an inverter (106) for feeding three-phase alternating currents of variable voltages/frequencies to the electric motor, a current command of an intermediate phase (a V-phase) having a smaller magnetic resistance of a stator core than those of other phases is subjected to a reducing correction by a correction unit (102) on the basis of the correction amount calculated by a current correction amount calculating unit (103), and the unbalanced three-phase alternating currents are fed to the AC motor (108), so that magnetic flux pulsations of a secondary electric angle and torque pulsations of the same order are reduced.