To reduce excessive cohesion of air or fuel vapor, in liquid fuel metering of a diaphragm carburetor for an internal combustion engine.

A liquid fuel feeding path communicates a pressurizing liquid fuel source and a metering chamber, and an engine fuel feeding metering path line has a first entrance connecting to the metering chamber and an injection exit connecting to a mixture ventilating path of a carburetor through a check valve. The injection exit meters and feeds a liquid fuel from the metering chamber to the mixture ventilating path. The first entrance is disposed so as to connected to a gas accumulating layer of the metering chamber and an exit area. When an engine and the carburetor installed on the engine are in a standard operating attitude direction of the engine, the exit is made to be the highest position in the metering chamber.