A step-down switching regulator includes a switching element performing switching in accordance with an input control signal to charge an inductor with an input voltage; a synchronous rectification element performing switching in accordance with an input control signal to discharge the inductor; a power supply circuit part generating and outputting a supply voltage; a capacitor connected to the connection of the switching element and the inductor; a first drive circuit part controlling the switching of the switching element in accordance with an input control signal; a second drive circuit part controlling the switching of the synchronous rectification element in accordance with another input control signal; and a control circuit part generating and outputting the control signals to the first and second drive circuit parts so that the predetermined constant voltage is output from an output terminal, wherein the second drive circuit part is supplied with power from the capacitor.