There is provided a multiphase switching power supply circuit in which an input terminal receives an input voltage, an output terminal outputs an output voltage, first to an Nth power stages each include an inductor having one end connected to the output terminal; a high-side switch that connects another end of the inductor to the input terminal; and a low-side switch that connects the other end of the inductor to a reference voltage, a switch signal controller supplies first to an Nth control signals to the first to Nth power stages, the first to Nth control signals complementarily turning on and off their corresponding high-side switches and low-side switches at a frequency fs, and a switch signal controller determines phases of the first to Nth control signals according to a ration between inductance values of the inductors included in the first to Nth power stages.