A switching power supply device includes: a switching output circuit configured to generate an output voltage from an input voltage; an oscillation circuit configured to generate a clock signal; a control circuit configured to control driving of the switching output circuit in synchronization with the clock signal; a pulse-by-pulse type overcurrent protection circuit configured to detect an overcurrent flowing through the switching output circuit to generate an overcurrent protection signal for forcibly stopping a switching operation of the switching output circuit; and a pulse skip circuit configured to perform a pulse skip operation of the clock signal in response to the overcurrent protection signal.