The present invention relates to an electrical control unit for an automobile of which standby electric current is smaller. In an electrical control unit for an automobile having a microcomputer (30), an input circuit, a driver circuit, and a power supply circuit (10), which is started by a wake-up signal from the circuit other than the ignition switch even when the ignition switch of the automobile is cut off, the microcomputer (30) is started by shifting the power supply circuit (10) from an inert state to an active state to generate the voltage for operating the microcomputer (30), and the predetermined processing is executed.