Disclosed is an electronic control unit capable of identifying an abnormality in a power supply voltage without narrowing the operating voltage range, and having minimal effects on cost and the circuit mounting surface area. The ECU includes a microcomputer containing an input terminal VCCin and an input terminal Vrin, a power supply IC that supplies a power supply voltage VCC to the input terminal VCCin, and as a reference-voltage-generator circuit a voltage-divider resistor and a voltage-divider resistor configuring a voltage-dividing circuit that outputs a sub-divided voltage Vc is sub-divided from the power supply voltage VCC, a capacitor coupled at one end to the input terminal Vrin and coupled on at the other end to ground, and a voltage isolation element coupled between the voltage-dividing circuit and the input terminal Vrin.