A wireless power relay apparatus , comprising: a relay power reception antenna configured to be electromagnetically coupled with a power transmission antenna of a power transmission apparatus in order to receive electric power from the power transmission apparatus ; a relay rectifier configured to convert the received electric power into a direct current, a relay inverter circuit configured to convert the direct current into an alternating current; a relay power transmission antenna configured to wirelessly transmit electric power of the obtained alternating current to a power reception apparatus , characterized by further comprising a relay amplitude modulator configured to transmit binary transmission data to the power transmission apparatus through electromagnetic coupling between the relay power reception antenna and the power transmission apparatus by modulating a voltage by means of a load modulation circuit in a circuit of the wireless power relay apparatus ; and a relay demodulator connected to the relay power transmission antenna and configured to receive binary reception data from the power reception apparatus by demodulating changes in the voltage of the alternating current input to the relay power transmission antenna , and a relay reverse control circuit configured to invert the binary reception data received by the relay demodulator and to cause the relay amplitude modulator to modulate the voltage by means of a load modulation circuit on the basis of the inverted binary reception data with a modulation level that is adapted to eliminate a variation in amplitude of a voltage at the power transmission antenna of the power transmission apparatus when the relay amplitude modulator is not transmitting the binary transmission data to the power transmission apparatus . a relay power reception antenna configured to be electromagnetically coupled with a power transmission antenna of a power transmission apparatus in order to receive electric power from the power transmission apparatus ; a relay rectifier configured to convert the received electric power into a direct current, a relay inverter circuit configured to convert the direct current into an alternating current; a relay power transmission antenna configured to wirelessly transmit electric power of the obtained alternating current to a power reception apparatus , characterized by further comprising a relay amplitude modulator configured to transmit binary transmission data to the power transmission apparatus through electromagnetic coupling between the relay power reception antenna and the power transmission apparatus by modulating a voltage by means of a load modulation circuit in a circuit of the wireless power relay apparatus ; and a relay demodulator connected to the relay power transmission antenna and configured to receive binary reception data from the power reception apparatus by demodulating changes in the voltage of the alternating current input to the relay power transmission antenna , and a relay reverse control circuit configured to invert the binary reception data received by the relay demodulator and to cause the relay amplitude modulator to modulate the voltage by means of a load modulation circuit on the basis of the inverted binary reception data with a modulation level that is adapted to eliminate a variation in amplitude of a voltage at the power transmission antenna of the power transmission apparatus when the relay amplitude modulator is not transmitting the binary transmission data to the power transmission apparatus . <EOS>