A control unit stops the supply of constant voltage into a vehicle electronic control unit in an abnormal state even though the ignition is off. A delay circuit for delaying an ignition OFF signal is installed outside the central processing unit. By controlling the power source to OFF by an output signal of the delay circuit or by the delay circuit for delaying by a longer time than that of a shut-off signal from the CPU due to the ignition OFF signal, and by the AND circuit of the output signal of the delay circuit and the shut-off signal from the CPU, and by an output signal of the AND circuit which is changed from high to low, the power supply from the power source IC is stopped.