In a DC regulated power supply realized as AC adapter or the like by a switching power supply, a reference voltage correction circuit, which estimates a voltage drop corresponding to a load current, corrects to increase an output voltage by changing a feedback reference value for regulation of the output voltage from a reference voltage source, in accordance with the load current sensed by the load current sensing circuit. Therefore, there occurs no negative effects that would be caused when output sensing wires are routed to a remote load. In addition, unlike the arrangement in which a reference-use rectifying circuit as well as a load-use rectifying circuit are provided, the arrangement of the switching power supply is not complicated. That is, in correcting a voltage drop, which occurs in power supply lines, corresponding to the load current, it is possible to easily perform a stable output voltage control unaffected by wire routing.