PURPOSE: To enhance the air velocity at high speed and improve the fuel feeding by arranging an air flow surface having prescribed aerodynamic characteristics and a fuel feeding orifice communicating with a fuel supply source via a conduit adjacent to a throat part in a venturi of a carburetor.

CONSTITUTION: A venturi 10 of a carburetor has a sidewall 12 partitioning a flow passage 14 extending between an inlet 16 and an outlet 18. A throat part 20 is formed in the intermediate part of the flow passage 14. In this case, an air flow surface 26 having prescribed aerodynamic characteristics and a fuel feeding orifice 28 communicating with a fuel supply source 30 via a conduit 38 are arranged in the sidewall 12 adjacent to the throat part 20. The air flow surface 26 is formed of an upstream part 32 positioned in the edge, a downstream part 34 positioned opposed thereto, and a surface part 36 positioned between them. This constitution can enhance the speed of the velocity of the air and improve the feeding of the fuel.