An excavator comprising: a power supply that converts AC power supply voltage from a commercial power supply into DC power supply voltage; a battery that charges or discharges power from the power supply; an inverter that converts DC power supply voltage to AC power supply voltage; an electric motor that has power supplied thereto, and is controlled, by the inverter; a first electrical circuit that supplies power to the inverter from the power supply; a second electrical circuit that joins from the battery to the first electrical circuit; an inverter relay arranged between the inverter and a junction point between the first electrical circuit and the second electrical circuit; a battery relay arranged between the junction point and the battery; and a power supply relay arranged between the junction point and the power supply.