PURPOSE: To surely atomize the injected fuel by providing a guide projecting portion for deflecting air toward the center of an intake air passage in a portion against which injected fuel bits at the time of opening a throttle valve out of the inner wall faces of the intake air passage.

CONSTITUTION: As the opening of a throttle valve 12 is increased, injected fuel 14a out of a fuel injection valve 14 does not hit against the throttle valve 12 but collides with the inner wall face of an intake air passage 10. In this case, an inclined guide projecting portion 15 which projects out so as to get gradually higher toward a collecting portion 8a is formed in the portion against which the injected fuel 14a out of the fuel injection valve 14 bits out of the inner wall faces of the intake air passage 10. Air flowing in the intake air passage 10 is deflected toward the center of the passage by the guide projecting portion 15. Also, the injected fuel which hits against the guide projecting portion 15 is deflected toward the center of the intake air passage 10 while being mixed with the air. Thereby, the injected fuel can be surely atomized.