In a power supply system for wirelessly supplying power between a power transmission device and a power reception device, the power transmission device includes a power transmission unit for generating supply power and transmitting the generated supply power to the power reception device; a power transmission side magnet for alignment with the power reception device; a magnetic sensor for detecting a magnetic force from a power reception side magnet provided in the power reception device; and a control unit for controlling the power transmission device. The power reception device includes: a power reception unit for receiving the supply power supplied from the power transmission device; the power reception side magnet for alignment with the power transmission device; and a control unit for controlling the power reception device. When the power transmission device and the power reception device are in close contact with each other, power is wirelessly transmitted from the power transmission unit to the power reception unit in a state in which the power transmission unit and the power reception unit are aligned by an attractive magnetic force between the power transmission side magnet and the power reception side magnet. When the power transmission device and the power reception device are apart from each other, the control unit of the power transmission device starts or stops power transmission from the power transmission unit according to a magnetic force detection signal from the power reception side magnet detected by the magnetic sensor.