Each cylinder of an internal combustion engine has two intake valves, two exhaust valves, a fuel injector and a spark plug. The fuel injector is vertically provided in a cylinder head of the engine such that a nozzle of the fuel injector is located in a central position of a combustion chamber. The spark plug is disposed between intake ports of the intake valves, so that an electrode of the spark plug is located near the nozzle of the fuel injector.