A constant-voltage power supply circuit unit that is fed from a vehicle-borne battery via a power switch and generates a predetermined constant-voltage output Vcc includes a power transistor and an output voltage regulating circuit unit. The output voltage regulating circuit unit includes a reference voltage generating circuit, a comparison amplifying circuit, a resistance circuit network, a non-volatile second data memory that selectively continues plural open/close elements provided in the resistance circuit network, and a temperature detector. The quantity of variation of output voltage with respect to ambient temperature detected by the temperature detector is estimated, and a setting voltage is corrected to be approximate to a predetermined output voltage, or conversion correction of AD conversion data is performed on the basis of voltage variation characteristics of an analog sensor.