A contactless power supply system includes a contactless power supply device and a power receiving device. Power is supplied from the contactless power supply device to the power receiving device while communication is performed therebetween. The power receiving device includes a power receiving coil unit, and a first communication unit that communicates with the contactless power supply device and attaches information having continuity to data transmitted to the contactless power supply device. The contactless power supply device includes a power supply coil unit, a second communication unit, and a power supply control unit that, when the second communication unit begins to receive data transmitted from the first communication unit, refers to the information having continuity attached to the continuously received data, and if continuity has been lost, performs correction to increase the output value of the power supplied from the power supply coil unit to the power receiving coil unit.