A switching power source device includes a switching power supply main body switching an input voltage via a switching element to obtain a predetermined DC output voltage, a control circuit performing on/off-driving of the switching element; and a capacitor connected to the control circuit to be charged by an external power supply via an activation switch circuit during activation and charged by a voltage generated in the switching power supply main body after completion of activation to supply a control power voltage to the control circuit. The control circuit further includes a latch circuit set according to a latch signal emitted when an abnormality is detected, to stop the driving of the switching element, a discharge circuit receiving the latch signal to be turned on and discharging charges accumulated in the capacitor, and a comparator resetting the latch circuit when the control power voltage decreases to an operation stop voltage.