To improve efficiency during light load.

A switching power supply A comprises: a switching control unit 17 for generating an output voltage Vout from an input voltage Vin by performing on/off control of switch elements 11 and 12 through a non-linear control system according to a comparison signal S1 and a timer signal S2; a main comparator 13 for generating the comparison signal S1 by comparing a feedback voltage Vfb corresponding to the output voltage Vout with a predetermined voltage Vref; a timer unit 14 performing one-shot output of the timer signal S2 when a predetermined fixed time has passed since on/off switching of the switch elements 11 and 12; and a reverse current detection unit 15 for detecting a reverse current to the switch element 12 to forcibly turn off the switch element 12. The timer unit 14 and the reverse current detection unit 15 are turned on when a pulse edge of the comparison signal S1 is generated, and turned off when each operation is completed.