A transmitting device having plural transmitting antennas , the transmitting device comprising: one transmission power supply for outputting electric power, whose frequency matches a resonance frequency of each of the transmitting antennas , on a basis of input power; plural switches respectively provided for the transmitting antennas , the switches being switchable in such a way as to connect or disconnect supply lines for supplying the electric power outputted by the transmission power supply to the transmitting antennas ; a parameter detecting unit comprised of a function of preventing breakage of the transmission power supply , the function being included by the transmission power supply , for detecting parameters regarding the transmission power supply , the parameters being changed as a receiving antenna of a receiving device gets close to the transmitting antennas ; and a switch control unit for estimating a position of the receiving antenna from a result of the detection performed by the parameter detecting unit , and for performing switching control on the switches in accordance with the position of the receiving antenna , wherein the transmitting device includes a matching circuit for matching impedance of the transmission power supply to that of each of the transmitting antennas , and wherein when the estimated position of the receiving antenna extends over those of two or more of the transmitting antennas , the switch control unit switches the switches in such a way as to connect the supply lines of the two or more of the transmitting antennas and causes the matching circuit to control a phase difference of the electric power outputted to the two or more transmitting antennas . one transmission power supply for outputting electric power, whose frequency matches a resonance frequency of each of the transmitting antennas , on a basis of input power; plural switches respectively provided for the transmitting antennas , the switches being switchable in such a way as to connect or disconnect supply lines for supplying the electric power outputted by the transmission power supply to the transmitting antennas ; a parameter detecting unit comprised of a function of preventing breakage of the transmission power supply , the function being included by the transmission power supply , for detecting parameters regarding the transmission power supply , the parameters being changed as a receiving antenna of a receiving device gets close to the transmitting antennas ; and a switch control unit for estimating a position of the receiving antenna from a result of the detection performed by the parameter detecting unit , and for performing switching control on the switches in accordance with the position of the receiving antenna , wherein the transmitting device includes a matching circuit for matching impedance of the transmission power supply to that of each of the transmitting antennas , and wherein when the estimated position of the receiving antenna extends over those of two or more of the transmitting antennas , the switch control unit switches the switches in such a way as to connect the supply lines of the two or more of the transmitting antennas and causes the matching circuit to control a phase difference of the electric power outputted to the two or more transmitting antennas . <EOS>