There is disclosed a spark-ignition engine having a combustion chamber in which cavities are formed. The cavities are in communication with each other via a communication passage. Air-fuel mixture is appropriately held in the cavities. Spark plugs are disposed near the centers of the cavities to ignite the mixture at plural positions. At the top dead center, the clearance between the top surface of the piston and the lower surface of the cylinder head is made small to minimize useless space. A large squish area is provided to effectively collect the mixture in the cavities. Since the combustible mixture is always held in the vicinities of the spark plugs, stable and rapid combustion can be realized.