A control apparatus for a vehicle electrical generator engine has

A control device such as an electronic control unit which controls the generator of a vehicle, measures the rotational speed of the engine and the rotational speed of the generator when the engine is idling and calculates and stores the ratio of speed values. Then, when the vehicle is moving, whenever the current value of the generator rotation speed is required, it is calculated on the basis of the value of the stored relation and the measured motor current regime. The electronic control unit processing load is reduced, since treatment of the measurement of the generator rotational speed is executed only during the engine idling.