A switching power supply apparatus includes a low-side switching control unit and a high-side switching control unit. The low-side switching control unit includes a low-side turn-off circuit that turns off a low-side switching element behind a delay time when reversal of the polarity of a winding voltage of a transformer is detected during a period in which a drive voltage signal is supplied to the low-side switching element. The high-side switching control unit includes a high-side turn-on delay circuit that delays a time from the time when the polarity of the winding voltage of the transformer is reversed to a time when a high-side switching element is turned on. The delay time of the low-side turn-off delay circuit is set so as to be shorter than the delay time of the high-side turn-on delay circuit.