A non-contact power feeder includes a plurality of power transmission coils disposed along a disposition surface, wherein a power receiving device that houses a power reception coil is disposed on the disposition surface, and a controller that determines a first traveling wave power, from among a plurality of traveling wave powers, that feeds the power transmission coil corresponding to the power receiving device based on a state of change of at least one of: actual transmitted power, from the plurality of traveling wave powers, transmitted from the plurality of power transmission coils to the power reception coil when power transmitted to the plurality of power transmission coils is changed, and reactive power, from the plurality of traveling wave powers, not transmitted from the power transmission coil to the power reception coil when the power transmitted to the plurality of power transmission coils is changed.