Fuel tank with fuel pump mounting structure

An insert ring is mounted on a resin-made fuel tank body, the insert ring has seat surfaces for mounting a fuel pump thereon and boss holes formed in the seat surfaces. An insert molded body is formed by insert molding of the insert ring using a first resin material while leaving the boss holes and the seat surfaces exposed. The insert molded body is inserted into an outer surface of the fuel tank body by insert molding using a second resin material which forms the fuel tank body.