A non-contact power supply system includes a power transmission device including a first resonance circuit having a first coil for transmitting electric power; and a power reception device including a second resonance circuit having a second coil for receiving the electric power. The system is configured to transmit and receive the electric power by a magnetic field resonance method, and to communicate between the power transmission device and the power reception device. The power transmission device includes a power transmission circuit for supplying an AC voltage to the first resonance circuit; a detection circuit configured to detect an amplitude of a current flowing through the first coil; and a control circuit configured to control the power transmission circuit to perform power transmission control of the electric power.