Abstract: In a four-stroke cycle engine in which a combustion chamber is formed by a piston accommodated in a cylinder block and a cylinder head disposed in the cylinder block and respective two suction valves and two exhaust valves are disposed in the combustion chamber, the combustion chamber is divided into two combustion sections each in which one of the suction valves and one of the exhaust valves are disposed. A mixture in a theoretical air-fuel ratio is fed into one of the divided combustion sections and a mixture in an air-fuel ratio corresponding to an engine load is fed into another one of the divided combustion sections, and the air-fuel ratio being changed in response to the engine load. In a case where the mixture in an air-fuel ratio includes an exhaust gas, substantially the same operation is performed, but in this case, the degree of opening of an exhaust gas recirculation valve is controlled so as to control the air-fuel ratio of the mixture.