In a switching power supply apparatus, a comparator outputs a first determination criterion signal based on a saw-tooth wave signal whose level fluctuates with a constant period and a detection voltage signal. An inverter subjects the first determination criterion signal to reverse processing, and outputs a second determination criterion signal. The comparator outputs a first switching judgment-use signal from a monitor signal and a threshold value, and the comparator outputs a second switching judgment-use signal from the monitor signal and the threshold value. An AND circuit outputs the first switching control signal from the first determination criterion signal and the first switching judgment-use signal, and the AND circuit outputs the second switching control signal from the second determination criterion signal and the second switching judgment-use signal.