A wireless power supply system (100) includes a power transmitter (101) and a power receiver (103). The power transmitter includes a power-transmitting coil (113) to which AC power of a frequency is input from a power source (111). The power receiver includes a power-receiving coil (121) magnetically coupled to the power-transmitting coil at a coupling coefficient, and a first power-receiving-side series element (123) coupled in series to the power-receiving coil and having imaginary impedance jZ S2i . In this wireless power supply system, the frequency and the imaginary impedance are determined so that impedance of a power-receiving side seen from the power source is independent of the coupling coefficient when the coupling coefficient changes.