A resonant contactless electric energy transmitter configured to contactlessly supply electric energy to an electric energy receiver, can include: (i) a high frequency power supply configured to generate a high frequency AC power with a frequency that is the same as a leakage inductance resonant frequency, where the leakage resonant frequency is obtained by detection of an output current of the high frequency power supply that corresponds to the high frequency AC power of a sequence of different frequencies during a frequency sweeping time period; and (ii) a transmitting resonant circuit comprising a transmitting coil, and being configured to receive the high frequency AC power from the high frequency power supply.