AIR-FUEL RATIO CONTROLLER OF INTERNAL COMBUSTION ENGINE

An air-fuel ratio controller, based on the emission air-fuel ratio of exhaust emission flowing into an exhaust emission control catalyst (19) in the exhaust emission passage (7) of an engine (1), the exhausted amount of at least one specific component contained in the exhaust emission flowing out of the exhaust emission control catalyst is estimated by using a model determined by considering the mass balance of the specific component, and the air-fuel ratio is controlled so that an estimated value becomes a target value.