A DC-DC converter includes a switching transistor connected to an inductor and a power input terminal, with the inductor connected to an output terminal, a synchronous rectification transistor connected to a junction node therebetween, a first electric current detector to detect whether or not an electric current flowing through the synchronous rectification transistor is larger than a first electric current, a second electric current detector to detect whether or not the electric current flowing through the synchronous rectification transistor is larger than a second electric current that is larger than the first electric current, and a selection mechanism to select one of the first and second electric current detectors in accordance with a control signal. The synchronous rectification transistor is turned off by outputting an output signal the selected current detector.