A self-oscillating switching regulator includes a control winding N3allowing a voltage to be induced therein by a magnetic flux created in a primary winding N1 of a high frequency transformer T, a capacitor C3 charged by the voltage induced in the control winding N3, a transistor Q2 that is turned off when the voltage across the capacitor C3 reaches a predetermined level, a switching element Q1 driven by the transistor Q2 to switch on or off an input current through the primary winding N1 of the high frequency transformer T, and a control winding adjuster for changing by switching the number of turns of the control winding N3 on the basis of the operating temperature.