CONTACTLESS POWER SUPPLY SYSTEM, POSITION ESTIMATION METHOD, MOBILE BODY, AND POWER SUPPLY DEVICE

Provided is a contactless power supply system (1) including a transmission-side resonance circuit (43) configured to transmit electric power, a reception-side resonance circuit (51) configured to receive the electric power from the transmission-side resonance circuit (43), an alternating current magnetic field generation circuit (6) configured to generate an alternating current magnetic field for detecting a relative positional relationship between the transmission-side resonance circuit (43) and the reception-side resonance circuit (51), and a magnetic field detector (7) configured to detect the alternating current magnetic field. The contactless power supply system (1) performs contactless electric power transmission of magnetic field resonance coupling between a ground-side device (2) and a mobile body (3). A frequency of the position detecting alternating current magnetic field is different from a resonance frequency of each of the transmission-side resonance circuit (43) and the reception-side resonance circuit (51).