A wireless power transfer system includes: a power supply primary coil capable of performing wireless power transfer; and a power supply secondary coil capable of performing the wireless power transfer between the power supply primary coil and the power supply secondary coil. The power supply secondary coil contains a secondary coil wire for the wireless power transfer and forms a secondary outer shape having a projecting surface on at least a part of the secondary outer shape, and the power supply primary coil and the power supply secondary coil are capable of performing the wireless power transfer, with the projecting surface of the secondary outer shape directed to the power supply primary coil.