A fuel supply apparatus mounting structure in which a set plate for holding a fuel supply apparatus is not corroded or deteriorated by the exposure to salt for thawing snow sprayed in winter in cold districts or to salt particles contained in sea wind in coastal areas is provided. The fuel supply apparatus mounting structure comprises a fuel pump 2 disposed within a fuel tank for pumping fuel to an internal combustion engine, a set plate 3 made of a synthetic resin and holding the fuel pump 2 and closing an opening hole 1a in the fuel tank 1, a gasket for maintaining airtight between the set plate 3 and the fuel tank 1, and a plate 4 for fastening the set plate 3 to the fuel tank 1, and a protective member 6, 8 made of a material which is not reacted, dissolved or deteriorated by a reaction product generated by a chemical reaction occurring between the plate 4 and the set plate 3 is inserted.