A switching regulator can convert an input voltage to a desired output voltage by ON-OFF controlling switching elements with PWM signals. The switching regulator can include a communication interface circuit that receives external operation instructions, an output voltage setting section that changes an output voltage to an output voltage setting value upon receiving an output voltage changing instruction from the outside, a voltage divider and an ADC that converts an error voltage into a digital error signal e[n], the error voltage being a difference between a reference voltage Vref and a detected output voltage value Vfb. The switching regulator can also include a controller that includes an operation control section for calculating a duty factor signal d[n] to determine an ON time proportion of the switching elements and an output voltage changing control section for controlling operation to change the output voltage.