A wireless power transmitter apparatus for a wireless power transmission system including a plurality of wireless power transmitter apparatuses and a plurality of wireless power receiver apparatuses, characterized in that the wireless power transmitter apparatus comprises: a power estimator that calculates a plurality of first estimated power values, each of the first estimated power values indicating estimated received power of a corresponding one of the wireless power receiver apparatuses when the wireless power transmitter apparatus transmits power to the plurality of wireless power receiver apparatuses, wherein the power estimator calculates each of the first estimated power values based on a signal level of a test signal received from each of the wireless power receiver apparatuses; a signal transmitting circuit that transmits each of the first estimated power values to a corresponding one of the wireless power receiver apparatuses; a signal receiving circuit that receives a plurality of second estimated power values from the wireless power receiver apparatuses, each of the second estimated power values indicating estimated received power of a corresponding one of the wireless power receiver apparatuses when other wireless power transmitter apparatuses of the wireless power transmission system transmit power to the wireless power receiver apparatuses; a power transmitter control circuit that determines pairing of the wireless power transmitter apparatuses and the wireless power receiver apparatuses for power transmission, based on the first and second estimated power values, so that estimated received power of each of the wireless power receiver apparatuses is equal to or higher than a predetermined threshold; and a power transmitting circuit that transmits power to one of the wireless power receiver apparatuses corresponding to the wireless power transmitter apparatus, based on the determined pairing. a power estimator that calculates a plurality of first estimated power values, each of the first estimated power values indicating estimated received power of a corresponding one of the wireless power receiver apparatuses when the wireless power transmitter apparatus transmits power to the plurality of wireless power receiver apparatuses, wherein the power estimator calculates each of the first estimated power values based on a signal level of a test signal received from each of the wireless power receiver apparatuses; a signal transmitting circuit that transmits each of the first estimated power values to a corresponding one of the wireless power receiver apparatuses; a signal receiving circuit that receives a plurality of second estimated power values from the wireless power receiver apparatuses, each of the second estimated power values indicating estimated received power of a corresponding one of the wireless power receiver apparatuses when other wireless power transmitter apparatuses of the wireless power transmission system transmit power to the wireless power receiver apparatuses; a power transmitter control circuit that determines pairing of the wireless power transmitter apparatuses and the wireless power receiver apparatuses for power transmission, based on the first and second estimated power values, so that estimated received power of each of the wireless power receiver apparatuses is equal to or higher than a predetermined threshold; and a power transmitting circuit that transmits power to one of the wireless power receiver apparatuses corresponding to the wireless power transmitter apparatus, based on the determined pairing.