NON-CONTACT POWER SUPPLY DEVICE

A power transmission device for a non-contact power supply device has: a transmission coil ; a coil connected in series to the transmission coil without joining to a reception coil during power transmission, said reception coil being included in a resonance circuit for a power reception device ; a power supply circuit that supplies, to the transmission coil , AC power having a switching frequency at which the transmission coil does not resonate; and a control circuit that controls the switching frequency and voltage of the AC power supplied to the transmission coil and controls whether or not both ends of the coil are short-circuited.