Abstract: Disclosed is a variable venturi type carburetor which is provided with a suction piston movable in a direction perpendicular to an air flow, in accordance with changes in the air flow, so as to vary the area of a venturi opening formed between the bottom end of the suction piston and a wall of the carburetor body facing the bottom end of the suction piston, for maintaining the speed of the air flow passing through the venturi opening substantially constant. The suction piston has a hole formed therein communicating the venturi opening with a suction chamber in which the suction piston is moved. The carburetor has a spring for urging the suction piston, but does not have any oil damper within the suction chamber. The shape of the venturi opening is so arranged that the increase of the area of the venturi opening in accordance with the displacement of the suction piston is gradually increased.