In a switching regulator, an inductor L1 (in FIG. 1) and an output capacitor C1 are connected on the output side of a series circuit consisting of a switching element (MOS transistor P1) and a synchronous rectification element (MOS transistor N1), and an N-channel MOS transistor Q1 is connected between an intermediate point of the inductor L1 and one terminal thereof. In addition, the frequency of oscillator 2 and the turning ON/OFF of MOS transistor Q1 are controlled by control unit 1. When output voltage Vout is to be altered, the switching frequency of MOS transistors P1 and N1 is increased, and the inductance of inductor L1 is reduced, whereby a fast output change is permitted. On the other hand, during ordinary constant output voltage operation, the switching frequency is reduced, and the inductance value is increased, whereby high efficiency is attained.