To present a DC-DC converter efficient in conversion and not requiring an external diode. The DC-DC converter includes a main NMOS transistor FET1 as a main switching device, a driver DVH1 for driving a gate terminal of the main NMOS transistor FET1, a capacitor C2 connected between a source terminal of the main NMOS transistor FET1 and a power source terminal of the driver DVH1, and an NMOS transistor FET3 connected between a route leading to an input power source and the power source terminal of the driver DVH1. The NMOS transistor FET3 does not conduct when the main NMOS transistor FET1 conducts, and conducts when the main NMOS transistor FET1 does not conduct.