The present invention performs correction appropriately according to errors in the fuel system and air system respectively and corrects both variations in the air-fuel ratio and torque. When the difference between a target air-fuel ratio and a real air-fuel ratio is equal to or below a predetermined value when feedback control based on the air-fuel ratio of an exhaust manifold 10A is in progress, the air-fuel ratio of a cylinder cyl—1 having the largest variation of angular acceleration is corrected to the rich side, for example, by increasing the amount of fuel. Angular acceleration per cylinder is then detected again and when the variation in angular acceleration among cylinders is not eliminated, it is judged that there is an error in the amount of air control of the cylinder having the largest variation and the amount of air, amount of fuel, ignition timing or the like are corrected.