In a maximum duty control state of a switching regulator control circuit, a period of time during which any one of a step-up switching circuit and a synchronous rectification switching circuit is always off is ensured, thereby preventing the switching efficiency from being remarkably deteriorated. In a maximum duty control state, a voltage difference is provided between a limiter voltage that is inputted to a comparator that controls the switching operation of the step-up switching circuit and a limiter voltage that is inputted to a comparator that controls the switching operation of the synchronous rectification switching circuit, to thereby ensure the period of time during which any one of the step-up switching circuit and the synchronous rectification switching circuit is always off.