A power sending loop coil disposed in a power sending device takes out electric energy from DC power and generates periodically-varying electromagnetic field resonance energy in a space. A power receiving loop coil disposed in a power receiving device takes out, as electric energy, the periodically-varying electromagnetic field resonance energy from the space and supplies electric power to a load. The power sending loop coil and the power receiving loop coil are coupled to each other through electromagnetic field resonant coupling, whereby electric power is wirelessly transferred from the power sending device to the power receiving device.