A power feeding system includes a power feeding device and a power receiving device. The power receiving device includes: a resonant circuit including a receiving coil, a resonant capacitor configured to resonate with the receiving coil, and a resonance control transistor configured to control a resonant state by changing an electrical connection state of the resonant capacitor; a rectifying diode configured to rectify received power by the receiving coil; and a resonance control unit configured to set the resonance control transistor to a non-conductive state based on the received power and power consumption of the load during a period including a subsequent conducting period during which a current flows to the rectifying diode, and which is estimated in a resonant state of the resonant circuit.