To include a leak-current detecting unit 21 that detects a zero-phase current flowing from an electric-motor driving device 100, which drives an electric motor 5 with electric power from an alternating-current power supply 1, or the electric motor 5 to a ground E2, a leak-current control unit 22 that, on the basis of the zero-phase current detected by the leak-current detecting unit 21, generates a control signal having cyclicity synchronized with the alternating-current power supply 1, and an anti-phase generating unit 23 that generates an anti-phase current that is in anti-phase to the zero-phase current on the basis of the control signal from the leak-current control unit 22, and outputs the anti-phase current.