PURPOSE: To provide a carburetor in which good accelerating operation and good emission can be performed while securing stable idling operation of an engine.

CONSTITUTION: A slow fuel system, in which fuel fed through a slow jet 23 is mixed with air fed from a slow air passage 27 so as to foam and is injected from an idle port 20 and a bypass port 21 to an intake passage 3, is provided. A pressure port 30 is arranged on an intake passage inside wall face in the position, to which an intake negative pressure of an engine is not applied when a throttle valve is opened at the predetermined valve travel or less while the intake negative pressure of the engine is applied when the throttle valve is opened at the predetermined valve travel or more, and the pressure port 30 is allowed communicate to with the slow air passage 27 via a pressure passage 31.