PURPOSE: To manufacture a composite pipe for transporting oils, etc., at a low cost, by seal-welding the side edges of a laminated sheet material comprising plural sheet materials, by winding it into a pipe shape, and by seam-welding the butted edges.

CONSTITUTION: A stainless steel strip 14 and a carbon steel strip 15 are uncoiled from pay-off reels 12, 13 by pay-off rollers 16, 17 and are overlapped with each other; then, both side edges 18 are welded by an electron beam welding along their faying surface; hereby, two strips 14, 15 are united into a laminated sheet 20 which is then sent out. This laminated sheet 20 is next formed into a pipe shape by a pipe forming-and-straightening rollers 21, 22, and the butted edges 18 are seam-welded 24 by a TIG welding method, etc., and a double-ply pipe 25 as a composite pipe is obtained. By the present method, a composite pipe for transporting oils, etc., comprising a stainless steel inner pipe and a carbon steel outer pipe, is easily manufactured.