To provide an AC rotary machine apparatus which can determine the operation stop of the control circuit of the other system with good accuracy. An AC rotary machine apparatus, including: a resolver is provided with a first system excitation winding, first system two output windings, a second system excitation winding, and second system two output windings, in which a magnetic interference occurs between a first system and a second system; a first system control circuit that applies AC voltage with a first period to the first system excitation winding; and a second system control circuit that applies AC voltage with a second period to the second system excitation winding, wherein the first system control circuit determines whether the operation of the second system control circuit stops, based on the components of the second period extracted from the first system output signals.