Abstract: A rotating member is provided on an output rotating shaft of an internal combustion engine to generate a signal corresponding to a predetermined cylinder group and an identification signal for identifying the particular cylinder group, and based on these signals, the particular cylinder group is identified. At the time of the start of internal combustion engine, fuel cut mode, or steady constant-speed running, the fuel injection amount of the particular cylinder among said particular cylinder groups is made different from that of other cylinders at a group injection timing such that the particular cylinder assumed on the basis of the cylinder group identification result is the reference, whether the assumption is true or false is judged from the present rotational variation and the cylinder group identification result, and the stroke phase of each cylinder is discriminated to make cylinder discrimination. At this time, the controlled variable relating to the rotational speed is regulated for other cylinders.