In a contactless power feeding system using a resonance method, an electric power receiving apparatus or an electric power transmitting apparatus is connected to a self-resonant coil and includes a capacitor having a variable capacitance. When electromagnetic resonance occurs at a prescribed frequency determined by the electric power transmitting apparatus, the capacitance of the capacitor is adjusted so as to maximize the electric power transmission efficiency during electric power feeding. Accordingly, deterioration in transmission efficiency can be suppressed even when the distance between the secondary self-resonant coil included in the electric power receiving apparatus and the primary self-resonant coil included in the electric power transmitting apparatus changes from a reference distance at the time of design.