A wireless power feeding system comprising a power transmitting apparatus and a power receiving apparatus, said wireless power feeding system being configured to supply electric power from said power transmitting apparatus to said power receiving apparatus in a wireless manner, said power transmitting apparatus comprising: a power transmission coil; and an inverter which is electrically connected with the power transmission coil, said power receiving apparatus comprising: a power reception coil; a DC/DC converter which is electrically connected with the power reception coil through a rectifier, and configured to supply a DC voltage to an electrical load; and a controlling device configured to control the DC/DC converter, to obtain a resonance frequency of the inverter and to estimate therefrom an overall resonant frequency of the system, to change a combined impedance between an impedance associated with the electrical load and an impedance associated with the DC/DC converter, by changing the DC voltage; characterized in that the controlling device is configured to control the DC/ DC converter (i) to change the combined impedance in a direction in which the combined impedance becomes less than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in series with the power reception coil or (ii) to change the combined impedance in a direction in which the combined impedance becomes greater than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in parallel with the power reception coil, in order to bring phase difference between the current of the power transmission apparatus and the current of the power reception apparatus corresponding to the estimated overall resonant frequency close to 180 degrees. a power transmission coil; and an inverter which is electrically connected with the power transmission coil, said power receiving apparatus comprising: a power reception coil; a DC/DC converter which is electrically connected with the power reception coil through a rectifier, and configured to supply a DC voltage to an electrical load; and a controlling device configured to control the DC/DC converter, to obtain a resonance frequency of the inverter and to estimate therefrom an overall resonant frequency of the system, to change a combined impedance between an impedance associated with the electrical load and an impedance associated with the DC/DC converter, by changing the DC voltage; characterized in that the controlling device is configured to control the DC/ DC converter (i) to change the combined impedance in a direction in which the combined impedance becomes less than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in series with the power reception coil or (ii) to change the combined impedance in a direction in which the combined impedance becomes greater than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in parallel with the power reception coil, in order to bring phase difference between the current of the power transmission apparatus and the current of the power reception apparatus corresponding to the estimated overall resonant frequency close to 180 degrees. a power reception coil; a DC/DC converter which is electrically connected with the power reception coil through a rectifier, and configured to supply a DC voltage to an electrical load; and a controlling device configured to control the DC/DC converter, to obtain a resonance frequency of the inverter and to estimate therefrom an overall resonant frequency of the system, to change a combined impedance between an impedance associated with the electrical load and an impedance associated with the DC/DC converter, by changing the DC voltage; characterized in that the controlling device is configured to control the DC/ DC converter (i) to change the combined impedance in a direction in which the combined impedance becomes less than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in series with the power reception coil or (ii) to change the combined impedance in a direction in which the combined impedance becomes greater than an excitation reactance when said power receiving apparatus comprises a capacitor which is electrically connected in parallel with the power reception coil, in order to bring phase difference between the current of the power transmission apparatus and the current of the power reception apparatus corresponding to the estimated overall resonant frequency close to 180 degrees.