PURPOSE: To prevent fuel from spitting and blowing-by by previously setting an area in which a predetermined engine speed area and a throttle valve opening area are overlapped each other as an area in which injected fuel is not taken in smoothly and changing injection start timing in this area.

CONSTITUTION: An air intake pipe 26 is connected via a reed valve 28 to an air intake port 30 opened at the side wall of the cylinder 12 of a 2 cycle internal combustion engine 10, and an electromagnetic type fuel injection valve 44 and a shutter type throttle valve 52 are provided at the air intake pipe 26. A pressure detector 50 as an intake air quantity detecting means, a potentiometer 54 for detecting the opening θ of a throttle valve, the rotational speed N of a crankshaft 20 and a rotational speed detecting means 56 for detecting a crank angle α are provided and output signals therefrom are input to a control unit 58. In an area in which a predetermined engine speed area and a predetermined throttle valve opening area are overlapped each other, i.e., an area wherein injected fuel is not intaken in smoothly, injection opening timing is changed to prevent the fuel from spitting.