A switching power supply circuit which is capable of reducing switching losses which occur when a switching element goes into the on state from the off state or goes into the off state from the on state. Switching elements are alternately actuated to on and off with dead times during which period both the switching elements are off. When one of the switching elements goes into the on state from the off state, a diode that is coupled in parallel with the switching element goes into the on state due to the energy released from a choking coil. Consequently, the switching element is switched on at a voltage of 0V (zero volts). Thus, switching losses can be reduced. Besides, when the switching element goes into the off state from the on state, the voltage rises moderately across the switching element as compared to the current passing through the switching element because of a capacitor that is coupled in parallel with the switching element. Thus, switching losses can be reduced. The same is true in the case of the other switching element.