WIRELESS POWER SUPPLY SYSTEM

A wireless power supply system (101) transmits power as magnetic field energy from a power supplying resonance coil (105) to a power receiving resonance coil (108) by resonating the power supplying resonance coil (105) and the power receiving resonance coil (108). The coil diameter (E) of the power receiving resonance coil (108) is set smaller than the coil diameter (D) of the power supplying resonance coil (105). Then, electromagnetic coupling between the power supplying resonance coil (105) and the power receiving resonance coil (108) is maintained in a stable state, and a space region where power can be transmitted in a state wherein power transmission efficiency is stabilized is expanded.