PURPOSE: To improve yield by eliminating completely defective molding of a lining layer, by a method wherein the inside of a pipe end leading to an end part of the lining layer of a steel pipe is cut, a core having a smaller diameter than the inside diameter of a cut part of the steel pipe and a larger diameter than the inside diameter of the lining layer is inserted through the pipe end and an end face of the core is stuck to the end face of the lining layer.

CONSTITUTION: After a lining layer 3b is formed of resin within a steel pipe main body of the steel pipe 1 with a flange, the resin is applied to a part up to a flange face of a pipe end from an end part of the steel pipe where the resin is not in existence and a flange lining layer is formed. Thus, the inside of the pipe end of the steel pipe main body 11 is cut up to the fixed diameter before infection molding and the inner circumference of the pipe end part is made into a perfect round. Then a core 5a having a smaller diameter than the inside diameter of the cut part of the steel pipe main body and larger diametwer than the lining layer 3b of the steel pipe main body 11 is inserted through the pipe end and the end face of the core 5a is stuck to a lining layer 7 of the steel pipe main body. Since injection molding of the resin is performed after that, the resin is filled properly within a cavity, defective molding is not generated at all.