A switching power supply device includes a switching power supply integrated circuit that includes a dead time generating unit that generates high-side and low-side drive signals having a dead time based on a PWM signal, a drive signal generating unit that generates first and second PWM signals based on the drive signals and a voltage of an output terminal, and a driver that includes high-side and low-side switch elements driven by the PWM signals; a filter that is connected to the output terminal; a first diode having a cathode connected to the source of the high-side switch element and an anode connected to the output terminal; and a second diode having a cathode connected to the source of the low-side switch element and an anode connected to the output terminal. The first and second diodes are arranged outside the switching power supply integrated circuit.