PURPOSE: To properly inject fuel changeably at every one rotation at the time of the two-cycle operation, and at every two rotations at the time of the four-cycle operation by switchably controlling a plural number of fuel injection nozzles which are arranged in a combustion chamber, according to the number of revolutions of an engine, respectively.

CONSTITUTION: An engine 21 is operated in two-cycle at the time of low speed, and it is operated in four-cycle at the time of high speed. In this case, in an combustion chamber 21 of the engine 21, there are respectively arranged, a first nozzle 22 which injects the fuel at every two rotations of an engine rotation shaft, along an wall face in the swirl flow direction, and a second nozzle 25 which injects the fuel at the timing of one rotation difference with respect to the first nozzle 22, to the part nearer to the center of the combustion chamber 21 than the part to which the fuel is injected by the first nozzle. At the time of two-cycle operation, the fuels are injected from the first an second nozzles 22, 25, respectively. At the time of the fourcycle operation, a valve 73 is switched over by a control unit 5 so that the fuel injection from the second nozzle 25 may be forbidden.