A device for supplying power from a vehicle battery to the outside is provided. The device includes an inverter circuit having a bridge circuit with multiple switching elements and that converts the received DC power into the AC power by switching the switching elements and that outputs the AC power. A controller controls an on/off state of each switching element through pulse width modulation. When an output AC output to the load has a value greater than a preset reference value or an input direct current input into the inverter has a value greater than a preset reference value, the controller changes a duty of each switching element to reduce an output AC voltage output from the inverter. When the reduced output AC voltage has a value equal to or less than a preset reference value, the controller stops a power conversion operation of the inverter.