COIL UNIT, NONCONTACT POWER RECEIVING DEVICE, NONCONTACT POWER FEEDING DEVICE, NONCONTACT POWER FEEDING SYSTEM, AND VEHICLE

In a noncontact electric power feeding system by means of a resonance method, an electric power receiving apparatus (110) includes a plurality of secondary self-resonant coils (112, 113). The noncontact electric power feeding system makes a switch between these secondary self-resonant coils (112, 113) to detect a distance between the electric power receiving apparatus (110) and an electric power transmitting unit, and selects, according to distance L as detected, a secondary self-resonant coil with high transfer efficiency for receiving electric power to accordingly feed electric power. In this way, distance L between the power receiving apparatus (110) and the power transmitting unit can be precisely detected including distances from longer ones to shorter ones, and the transmission efficiency in transmitting electric power in a noncontact manner by means of the resonance method can be improved.