A power feeding device of a non-contact charging device for feeding power to a power receiving device in a non-contact fashion, the power feeding device comprising: a power factor improvement circuit adapted for converting an AC power supply to DC, and for improving a power factor, a smoothing capacitor connected to an output end of the power factor improvement circuit, an inverter circuit which includes a plurality of switching elements (21, 23, 26, 28), and is adapted for generating an AC signal by switching each of the switching elements using a voltage of the smoothing capacitor as a power supply, a power feeding section which includes a resonant capacitor and a first inductor connected to an output end of the inverter circuit, and is adapted for feeding power generated between the first inductor and a second inductor provided in the power receiving device to the power receiving device based on the AC signal, a control circuit adapted for modulating a duty ratio of each of the switching elements (21, 23, 26, 28) of the inverter circuit in synchronization with the AC power supply when the power feeding section feeds the power to the power receiving device, characterized in that said control circuit is further adapted for performing said modulation such that the duty ratio of each of the switching elements (21, 23, 26, 28) is less than a predetermined reference during a positive half-wave of a voltage ripple at the smoothing capacitor and greater than the predetermined reference during a negative half-wave of the voltage ripple at the smoothing capacitor, and such that in a range higher than a range where an input power characteristic curve relative to the duty ratio is substantially linear, a difference between a maximum of the duty ratio and the reference is greater than a difference between the reference and a minimum of the duty ratio. a power factor improvement circuit adapted for converting an AC power supply to DC, and for improving a power factor, a smoothing capacitor connected to an output end of the power factor improvement circuit, an inverter circuit which includes a plurality of switching elements (21, 23, 26, 28), and is adapted for generating an AC signal by switching each of the switching elements using a voltage of the smoothing capacitor as a power supply, a power feeding section which includes a resonant capacitor and a first inductor connected to an output end of the inverter circuit, and is adapted for feeding power generated between the first inductor and a second inductor provided in the power receiving device to the power receiving device based on the AC signal, a control circuit adapted for modulating a duty ratio of each of the switching elements (21, 23, 26, 28) of the inverter circuit in synchronization with the AC power supply when the power feeding section feeds the power to the power receiving device, characterized in that said control circuit is further adapted for performing said modulation such that the duty ratio of each of the switching elements (21, 23, 26, 28) is less than a predetermined reference during a positive half-wave of a voltage ripple at the smoothing capacitor and greater than the predetermined reference during a negative half-wave of the voltage ripple at the smoothing capacitor, and such that in a range higher than a range where an input power characteristic curve relative to the duty ratio is substantially linear, a difference between a maximum of the duty ratio and the reference is greater than a difference between the reference and a minimum of the duty ratio.