PURPOSE: To enable an engine to be properly controlled even in a transient engine operation region upon changing over cylinders by controlling a combustibility govering and controlling target after providing a combustibility govering and controlling value corresponding to a cylinder number changeover operation region corresponding to an engine operation region besides a combustibility govering and controlling value corresponding to a required operating cylinder number region.

CONSTITUTION: Signals concerning: Opening of a throttle valve 8, engine cooling water temperature by a cooling water temperature detecting sensor 26, intake air negative pressure by an intake air negative pressure sensor 27, number of engine revolutions detected by an ignition coil 28, and a TDC signal from an engine top dead point, etc., are inputted to a control unit 25 composed of a microcomputer. Said unit 25 outputs a reduced number of operating cylinder instruction signal and a full cylinder operation instruction signal as a number of operating cylinder changeover instruction signal to solenoids 23, 24, while outputting an injection pulse signal to a fuel injection valve 7. Said solenoids 23, 24 serve to interrupt fuel supplies to respective cylinders of an engine being forgets of inoperative cylinder and to changeover the number of cylinders to be operated based on the number of operating cylinder changeover instruction signal issued from valve driving control devices 21, 22 and a number of operating cylinder c hangeover instruction outputting means.