To provide a switching power supply device that prevents a change in output voltage in both of PWM (pulse width modulation) control and PFM (pulse frequency modulation) control.

The switching power supply device 100 includes: a switching element 1 for performing a switching operation; an output voltage generation circuit 22; a transformer reset detection circuit 12 for generating a transformer reset signal Vreset; a secondary-side on-time signal generation circuit 13; a feedback control circuit 11 for generating a feedback signal VEAO; a switching element drive circuit 3 for controlling the switching operation of the switching element 1 according to the feedback signal VEAO; and an output voltage correcting signal generation circuit 15 for generating an output voltage correcting signal Vcomp1 from the feedback signal VEAO and a secondary-side on-time signal V2on, and supplying the output voltage correcting signal to the feedback control circuit 11.