To provide a step-up/down switching regulator control circuit and the step-up/down switching regulator which are stable in a wide output voltage range from step-up to step-down. According to the present invention, a plurality of phase compensating circuits, a circuit for detecting an input/output voltage, and a switching circuit are disposed in an error amplifier circuit, and a phase compensating circuit is switched to an optimum phase compensating circuit upon detecting the input/output voltage. In addition, the plurality of phase compensating circuits are structured in the exterior of the step-up/down switching regulator control circuit, and a proper phase compensating constant can be set according to an intended purpose.