A wireless power supply system includes a power transmission device provided on a ground side and a power receiving device mounted on a vehicle, the power transmission device transmitting, to the power receiving device via a wireless connection, electric power controlled by an inverter circuit, wherein the power receiving device transmits a power supply command signal to the power transmission device in a first cycle by use of a radio signal. The power transmission device includes a power transmission coil current detection means for detecting a power transmission coil current flowing through a power transmission coil and controls an output voltage of the inverter circuit based on the power supply command signal and the power transmission coil current detected by the power transmission coil current detection means in a second cycle shorter than the first cycle.