A coil unit includes a resonant coil establishing electromagnetic field resonant coupling with an external resonant coil provided external to a vehicle. The resonant coil includes an outer side coil extending along a circumference of a first winding center, centered about the first winding center, and an extension extending from the outer side coil into a region surrounded by the outer side coil. The resonant coil is formed such that an anti-node of the resonant coil that is an area of an anti-node of AC current flowing through the resonant coil, is located at the extension when electromagnetic field resonant coupling is established between the external resonant coil and the resonant coil.