A switching power supply device includes: a power factor correction circuit having a step-up chopper circuit including a chopper switching element and a power factor correction control unit controlling a switching operation of the chopper switching element; a DC/DC converter having a transformer, a switching circuit, a rectifier circuit, a smoothing circuit, and a DC/DC converter control unit; and a control ON/OFF circuit controlling the ON/OFF states of an output voltage of the DC/DC converter circuit. The switching circuit is provided at a primary winding side of the transformer. The rectifier circuit and the smoothing circuit are provided at a secondary winding side of the transformer. The control ON/OFF circuit controls the ON/OF states of the output voltage of the DC/DC converter circuit by controlling the power factor correction control unit and the DC-DC converter control unit based on an external signal.