An inverter and power transmission coils are connected such that currents flow in opposite directions to each other when selection switches of respective power transmission coils adjacent to each other, out of a plurality of power transmission coils disposed in the movement direction of a mobile body, are caused to be conductive. The difference in currents flowing in the opposite directions is measured, and compared with a threshold, whereby whether or not a power reception coil mounted to the mobile body is present above the power transmission coil can be determined.