A starting power securing structure of an electric power supply device includes a built-in battery that is mounted on the electric power supply device, an operation control portion that is mounted on the electric power supply device and controls the operation of the electric power invert portion, and a discharging control portion that is provided in the electric vehicle and controls the discharging of the driving battery, wherein the driving battery, the operation control portion and the first connection plug are electrically connected, and the electric power of the built-in battery is supplied to the operation control portion and the first connection plug, whereby the electric power is supplied to the discharging control portion via the first connection plug while the electric power invert portion can be operated, and electricity can be transmitted from the electric vehicle to the electric power supply device.