Cylinder heads are each provided with a fuel injection valve, and an addition nozzle for adding fuel for activating an exhaust purifying catalyst to an exhaust manifold. There exists a non-exhaust period in which an exhaust gas does not flow out to exhaust passages from the exhaust manifolds during an operation of an engine. An ECU controls the addition nozzles in such a manner that the addition nozzles execute a fuel addition during periods except the non-exhaust period. Accordingly, the fuel added to the exhaust manifolds for activating the catalysts is avoided from collecting on a wall surface of an exhaust system without getting on an exhaust stream.