PURPOSE: To improve corrosion resistance of a device and prevent deterioration of its fuel metering accuracy, in the device used with mixed fuel from gasoline and alcohol, by applying electroless plating to a part contacted to the mixed fuel and performing ball burnishing work to a necessary place.

CONSTITUTION: In a carburetor used with mixed fuel, the mixed fuel in a float chamber 10 is jetted into a Venturi part 7 from a main nozzle 8 through a main jet 11 and emulsion tube 12. While the mixed fuel is partially jetted into an intake passage 2 from an air bleed 16 or the like through a slow jet 14. Here an internal surface of members, adhesively contacted with fuel and its vapor, such as each jet 11, 14, nozzle 8, fuel pipe line, etc., is applied with chrome or nickel electroless plating, and then applied with heat treatment, finally swept out absorbed hydrogen. Further for the nozzle 8 and jets 11, 14, fuel metering part in the above members, ball burnishing work is performed after plating.