In a control circuit which turns on/off the switching device elements included in a synchronous rectifier step-down switching regulator, a hysteresis comparator compares the detection voltage that corresponds to the output voltage of the step-down switching regulator with a first threshold voltage and a second threshold voltage. A light-load detection circuit detects whether or not a load is in the light-load state. A driver circuit turns on/off the switching device elements according to the pulse signal output from the hysteresis comparator. Upon the light-load detection circuit detecting the light-load state, the hysteresis comparator shifts the second threshold voltage toward the higher-voltage side by a predetermined voltage difference.