To provide a rotary throttle valve-type carburetor excellent in durability and to be normally stably and reliably operated.

A throttle valve 2 having a throttle hole 5 is rotatably and liftably inserted in a cylindrical valve chamber 9 vertically extending while intersecting an intake passage 35 laterally perforating an aluminum alloy-made carburetor main body 31, a fuel nozzle 6 communicated with a constant pressure fuel chamber 46 supported on the bottom wall of the valve chamber 9 is projected to the throttle valve 5, and a needle 3 supported on the throttle valve 2 is inserted in the fuel nozzle 6 to adjust the opening of a fuel injection hole 6a. A resin-made cover plate 20 is pinched between the upper end wall of the carburetor main body 31 and a bracket 13 made of metal such as aluminum alloy, zinc alloy, or the like, the bracket 13 is fitted around a boss part 20a for supporting a valve shaft 2a projecting upwardfrom the resin-made cover plate 20, a throttle valve lever 10 is connected to the upper end of the valve shaft 2a, and a cam mechanism is formed between the upper surface of the bracket 13 and the lower surface of the throttle valve lever 10.