A terminal device comprising: a secondary-side coil configured to receive electric power transmitted from a primary-side coil of an electric power feeding device; a rectifier unit configured to rectify reception electric power obtained by the secondary-side coil; a secondary-side communication unit configured to communicate with the electric power feeding device, the secondary-side communication unit being configured to receive a small electric power for start-up from the electric power feeding device, the small electric power being electric power that enables communication between the secondary-side communication unit and the electric power feeding device, the small electric power being smaller than or equal to 5W and a range of settable levels of electric power being larger than or equal to 5W, to transmit a signal to the electric power feeding device which confirms the electric power of the electric power feeding device, to receive an information which indicates the electric power from the electric power feeding device, a regulator including a first regulator and a second regulator, the regulator being configured to convert the reception electric power rectified by the rectifier unit to electric power of a predetermined voltage, and to conduct conversion by a first conversion method of the first regulator or by a second conversion method of the second regulator, a control unit configured to determine whether the electric power is larger than or equal to a threshold value on the basis of the information received by the secondary-side communication unit and to instruct to use the first regulator if the transmission electric power level is larger than or equal to the threshold value and to use the second regulator if the transmission electric power level is smaller than the threshold value. a secondary-side coil configured to receive electric power transmitted from a primary-side coil of an electric power feeding device; a rectifier unit configured to rectify reception electric power obtained by the secondary-side coil; a secondary-side communication unit configured to communicate with the electric power feeding device, the secondary-side communication unit being configured to receive a small electric power for start-up from the electric power feeding device, the small electric power being electric power that enables communication between the secondary-side communication unit and the electric power feeding device, the small electric power being smaller than or equal to 5W and a range of settable levels of electric power being larger than or equal to 5W, to transmit a signal to the electric power feeding device which confirms the electric power of the electric power feeding device, to receive an information which indicates the electric power from the electric power feeding device, a regulator including a first regulator and a second regulator, the regulator being configured to convert the reception electric power rectified by the rectifier unit to electric power of a predetermined voltage, and to conduct conversion by a first conversion method of the first regulator or by a second conversion method of the second regulator, a control unit configured to determine whether the electric power is larger than or equal to a threshold value on the basis of the information received by the secondary-side communication unit and to instruct to use the first regulator if the transmission electric power level is larger than or equal to the threshold value and to use the second regulator if the transmission electric power level is smaller than the threshold value.