Abstract: This application discloses a variable-venturi carburetor of an internal combustion engine. The carburetor comprises: a variable venturi; a pressure source for actuating the venturi; a working chamber into which the pressure is introduced from the pressure source so as to actuate the venturi; a pipe which connects the pressure source and the working chamber; and a diaphragm type pressure control valve, the inlet of the valve being communicated with the atmosphere, the outlet of the valve being connected to the pipe, the diaphragm chamber of the valve being communicated with the intake pipe of the engine at a portion between the throttle valve and the venturi.