PURPOSE: To attain prevention of malfunction at cranking of a car by adding a capacitor and a resistor being elements of time constant to a CR filter in a reset circuit of an electronic device for car so as to constitute a constant resistance circuit.

CONSTITUTION: An Acc power voltage from a key switch 39 charges a capacitor C1 via a diode D1 and the voltage is held for a time decided by the capacitor C1 and a resistor R3. The voltage is inputted to a CMOS40 using a voltage VC formed from a battery voltage by a power supply section as the power supply. The constant resistance circuit is constituted by adding the capacitor C10 and the resistor R10, the fluctuation of the voltage VC is injected to the input of the CMOS40 by the capacitor C10 and the resistor R40 so as to cancel it so as not to be given to the output side. Even if the power supply voltage VC is fluctuated at cranking of an engine. The stable operation of the circuit is attained.