A current mode control type switching power supply device includes a first switch having a first terminal connected to a first application terminal to which an input voltage is applied, and a second switch having a first terminal connected to a second terminal of the first switch and a second terminal connected to a second application terminal to which a predetermined voltage lower than the input voltage is applied. A current sensor is configured to sense current flowing in the second switch. A controller configured to control the first switch and the second switch, wherein the controller is configured to control the first switch and the second switch independently of a difference between the input voltage and an output voltage and in addition in accordance with the current sensed by the current sensor.