A DC-DC converter applicable to a wide input voltage range. An error amplifier compares a divided voltage, which is generated by dividing output voltage with a plurality of resistors, and a reference voltage to generate an error signal. A voltage source generates an offset signal by offsetting the error signal. A PWM comparator compares the offset signal with a triangular wave signal to generate a drive signal for controlling activation and inactivation of a first output transistor and a second transistor at a duty corresponding to the comparison result. An offset controller determines the ratio between the output voltage and the input voltage and controls the offset voltage of the voltage source in accordance with the determination.