Abstract: A carburetor for an automobile engine of a sliding throttle valve type, wherein a throttle valve guide cylinder is connectively provided at one side of an air-intake barrel, in which an air-intake passage is formed and at which a main nozzle is open, and a throttle valve which opens and closes the air-intake passage on the main nozzle is provided inside the throttle valve guide barrel in a sliding manner, the carburetor being further provided with a movable part in the throttle valve, which is capable of increasing an amount of mixture air to be usually adjusted by the throttle valve in such a manner that the movable part may be actuated when a negative pressure of a certain definite value and above develops at the down-stream side of the throttle valve due to reduction in speed of the engine.