A DC-DC converter has a switching circuit including switching elements at the high-side and at the low-side, an inductor connected to the output end of the switching circuit, a smoothing capacitor connected to the inductor, a switching control circuit for supplying a switching pulse to the switching elements, and a circuit. The circuit detects that a state that the switching element at the high side is switched off and the switching element at the low side is switched on is maintained for a predetermined period or longer. In this case, the circuit forcibly switches off the switching element at the low side.