To provide a winding changeover device of a three phase AC motor, which can be realized with a simple structure, without a shock when winding is changed over under a condition of acceleration and deceleration and to provide an inverter device.

The winding changeover device of the AC motor includes: an AC motor equipped with a plurality of windings at every phase; winding changeover means for changing over the plurality of windings; and the inverter device for driving the AC motor. The inverter device includes: a winding changeover command signal generator for outputting a winding changeover command signal; a constant changer for changing over a plurality of incorporated motor constants of the AC motor in accordance with an output of the winding changeover command signal; and a current detection value correction computing unit for correcting a detection value of the motor current flowing in the AC motor in accordance with a change of the motor constant.