A power receiver (100, 100A) comprising: a first secondary-side resonant coil, including a resonant coil part, a first terminal and a second terminal, that receives electric power from a primary-side resonant coil through magnetic field resonance generated between the primary-side resonant coil and the first secondary-side resonant coil, the first terminal and the second terminal being respectively provided on both ends of the resonant coil part; a capacitor inserted in series with the resonant coil part of the first secondary-side resonant coil; a rectifier circuit, coupled to the first terminal and the second terminal, that rectifies alternating-current power input from the first secondary-side resonant coil; a smoothing circuit coupled to an output side of the rectifier circuit; a pair of output terminals (160A, 160B) coupled to an output side of the smoothing circuit; a switch coupled in parallel to the capacitor or coupled in series between the rectifier circuit and one of the first terminal and the second terminal of the first secondary-side resonant coil; characterised by a drive controller that drives the switch based on a first PWM drive pattern determined by a first duty cycle and by a first frequency that is less than or equal to a frequency of the magnetic field resonance, the first duty cycle being set based on a first efficiency of electric power reception of the first secondary-side resonant coil, a first rated output of a first load coupled to the pair of output terminals (160A, 160B), a second efficiency of electric power reception of a second secondary-side resonant coil of another power receiver that receives electric power from the primary-side resonant coil through magnetic field resonance generated between the primary-side resonant coil and the second secondary-side resonant coil, and a second rated output of a second load to which the electric power is supplied from the other power receiver, wherein, when a first value obtained by dividing the first rated output by the first efficiency of electric power reception is less than a second value obtained by dividing the second rated output by the second efficiency of electric power reception, the first duty cycle is set to be a predetermined duty cycle that is less than a first initial value, and wherein the predetermined duty cycle is a duty cycle by which a balance between the electric power that the first load receives and the electric power that the second load receives is improved relative to a balance of a case where the first duty cycle is the first initial value. a first secondary-side resonant coil, including a resonant coil part, a first terminal and a second terminal, that receives electric power from a primary-side resonant coil through magnetic field resonance generated between the primary-side resonant coil and the first secondary-side resonant coil, the first terminal and the second terminal being respectively provided on both ends of the resonant coil part; a capacitor inserted in series with the resonant coil part of the first secondary-side resonant coil; a rectifier circuit, coupled to the first terminal and the second terminal, that rectifies alternating-current power input from the first secondary-side resonant coil; a smoothing circuit coupled to an output side of the rectifier circuit; a pair of output terminals (160A, 160B) coupled to an output side of the smoothing circuit; a switch coupled in parallel to the capacitor or coupled in series between the rectifier circuit and one of the first terminal and the second terminal of the first secondary-side resonant coil; a drive controller that drives the switch based on a first PWM drive pattern determined by a first duty cycle and by a first frequency that is less than or equal to a frequency of the magnetic field resonance, the first duty cycle being set based on a first efficiency of electric power reception of the first secondary-side resonant coil, a first rated output of a first load coupled to the pair of output terminals (160A, 160B), a second efficiency of electric power reception of a second secondary-side resonant coil of another power receiver that receives electric power from the primary-side resonant coil through magnetic field resonance generated between the primary-side resonant coil and the second secondary-side resonant coil, and a second rated output of a second load to which the electric power is supplied from the other power receiver, wherein, when a first value obtained by dividing the first rated output by the first efficiency of electric power reception is less than a second value obtained by dividing the second rated output by the second efficiency of electric power reception, the first duty cycle is set to be a predetermined duty cycle that is less than a first initial value, and wherein the predetermined duty cycle is a duty cycle by which a balance between the electric power that the first load receives and the electric power that the second load receives is improved relative to a balance of a case where the first duty cycle is the first initial value.