A switching-control circuit to control a switching operation of a transistor, having an input electrode applied with the input voltage and an output electrode connected to a load via an inductor, to generate an output voltage of a target level from an input voltage, includes: a voltage-generating circuit to generate a slope voltage based on the output voltage in each of a switching period of the transistor, the slope voltage changing with a slope corresponding to the output voltage; an adding circuit to add the slope voltage to a reference voltage, indicating a reference of the output voltage of the target level, or a feedback voltage corresponding to the output voltage; and a drive circuit to perform the switching operation of the transistor, when a level of either one voltage, added with the slope voltage, of the reference and feedback voltages reaches a level of an other voltage thereof.