An air valve type carburetor of the kind in which a throttle valve is disposed in the downstream portion of a barrel interconnected to an engine via an intake manifold; a main nozzle is disposed upstream of the barrel and is connected to a jet of a float chamber; an air horn disposed on the barrel is connected to an air cleaner via an air connector; an air valve is disposed at the upper part of the main nozzle, faces at its tip the nozzle and is connected to the base end of a metering needle which is inserted into a through-hole of the air horn for free vertical movement therein; and a shield plate is fixed to the shank of the metering needle so as to prevent pressure pulsations inside the air connector from entering the through-hole and being applied to the surface of the fuel.