A DC-DC converter to convert an input voltage into a predetermined voltage includes a first switching device to provide energy for an inductor; a second switching device to discharge the energy from the inductor to an output terminal; an error amplifier to amplify an error voltage between a first reference voltage and a monitoring voltage obtained by dividing an output voltage output from the output terminal; a set signal generation circuit including a first comparator into which a second reference voltage and an output of the error amplifier are input; a reset signal generation circuit; a control circuit into which an output from the set signal generation circuit and an output from the reset signal generation circuit are input; and a detection circuit to detect a switching frequency of an electric power supply, wherein a characteristic of the first comparator is changed according to the switching frequency.