In the switching power supply device, a controller has a first state in which it keeps a first switch on and a second switch off, a second state in which it keeps the first switch off and the second switch on, a third state in which it keeps the first and second switches off, and a fourth state in which it keeps a voltage at a connection node between the first and second switches lower than in the third state. The controller has a first mode in which the controller repeats the first to fourth states at a first cycle, and a second mode in which the controller repeats the first to fourth states at a second cycle longer than the first cycle.