An external resistor is connected to a detection terminal. A pulse modulator is configured to generate a pulse signal SPWM having a duty ratio adjusted such that the output voltage VOUT of a DC/DC converter approaches a target value. A pulse modulator is configured to switch the pulse signal SPWM to a level that corresponds to the off level of the switching transistor according to a detection voltage VS that develops at the detection terminal. A short-circuit detection circuit is configured to generate a short-circuit detection signal which is asserted when the detection voltage VS is higher than a predetermined threshold voltage VTH after a judgment time elapses after the pulse signal SPWM is switched to an on level that corresponds to the on state of the switching transistor. When the short-circuit detection signal is asserted, the pulse modulator is configured to switch the pulse signal SPWM to the off level.