A storage section stores three-phase detection currents and outputs them as three-phase storage detection currents and also stores three-phase voltage commands and outputs them as three-phase storage voltage commands. A second voltage command calculating section outputs three-phase voltage commands on the basis of the three-phase storage detection currents and the three-phase storage voltage commands, which are acquired from the storage section, and the three-phase detection currents acquired from a current detecting means. A voltage command output means outputs, to a voltage application means, three-phase voltage commands acquired on the basis of the three-phase voltage commands from the storage section and the three-phase voltage commands from the second voltage command calculating section. The voltage application means applies a voltage to an AC rotary machine on the basis of the three-phase voltage commands from the voltage command output means.