To eliminate any variance by covering a circumferential wall portion of at least a head portion of a fuel regulating needle valve by a synthetic resin, and forming a knurl thereon at the same time.

In a carburetor of an internal combustion engine in which a fuel regulating needle valve 10 with a tip needle 12 protruded in the middle of a fuel passage leading from a fuel chamber to a fuel injection nozzle of a suction passage is screwed and supported by a carburetor body 2, and a cap regulating the maximum fuel quantity is fitted to the head portion 16 of the fuel regulating needle valve 10, the synthetic resin is molded to cover a metal body 16a of dissimilar section of at least the head portion 16 of the fuel regulating metal needle valve 10, and the knurl 16c is integrated with an outer circumferential surface.