PROBLEM TO BE SOLVED: To effectively perform combustion by compression self-ignition in a wider operating region while suppressing the occurrence of knocking. SOLUTION: The flow state of intake/exhaust is controlled so that burnt gas exhausted from preceding cylinders 2A, 2D is led into succeeding cylinders 2B, 2C in a partial load region of an engine. A combustion state control means 44 controls to perform combustion of the succeeding cylinders 2B, 2C by compression self-ignition in at least a partial operating region out of an operating region set to a special operation mode. In a high load side region in the compression self-ignition region, the combustion state control means 44 controls to lead fresh air into the succeeding cylinders 2B, 2C in addition to the burnt gas led out of the preceding cylinders 2A, 2D by making the air-fuel ratio of the preceding cylinders 2A, 2D relatively rich compared to a lower load side region and opening a fresh air lead-in intake valve 31a for leading the fresh air into the succeeding cylinders 2B, 2C. COPYRIGHT: (C)2004,JPO