A coil unit includes a coil and an accommodation case accommodating the coil. The coil is formed of a coil wire wound around a winding axis. A hollow portion is formed in a position in which the winding axis passes. The coil includes an outer peripheral portion located in an outer peripheral edge of the coil, and an inner peripheral portion located along an inner peripheral edge of the coil. A voltage on the inner peripheral portion is higher than a voltage on the outer peripheral portion.