To eliminate a change of metering precision of a slow fuel due to corrosion of slow jet by rancidity gasoline.

A silica film 5 is formed on a surface throughout a range L extending from the relative oil surface position E of a slow jet 1 to above. The members of a tube part 2 and a jet part 3 are made of brass. Through anticorrosive operation of the silica film 5, the tube part 2 and the jet part 3 are prevented from corrosion by anticorrosive. The thickness h1 of the silica film 5 is higher than thickness h2. Namely, the silica film 5 is thicker than the inner wall of the tube part 2 by the inner wall of the jet part 3 and effective anticorrosive operation is effectively acted.