A semiconductor circuit device includes a current detecting circuit that converts an inductor current into a voltage and outputs the voltage as a current detection voltage, a differential amplifier circuit that amplifies a difference between a voltage corresponding to the output voltage and a reference voltage, a level shifter, and a comparing circuit that compares the current detection voltage with a level-shifted voltage and outputs a switching signal for a switching device. The differential amplifier circuit includes a MOS transistor provided between a power supply node and an output node. The level shifter level-shifts a voltage at the output node of the differential amplifier circuit to a low potential side and outputs the level-shifted voltage.