The present invention is intended to provide a DC-DC converter, in which the relationship between the duty ratio of a drive signal and the output DC voltage is nonlinear, being characterized in that the relationship between an error signal and the output DC voltage is linear, and that the design of stabilizing the feedback system is facilitated. The DC-DC converter comprises an error-amplifier circuit for generating the error signal that is obtained by amplifying the error between the output and a target value, an oscillating circuit for generating a triangular wave signal having an amplitude corresponding to the error signal, and a comparison circuit for comparing the triangular wave signal with a reference signal having a predetermined value and for generating the drive signal to turn ON/OFF a switching device.