Abstract: A resin sheet that is comprised of a thermoplastic resin capable of being thermally welded to a lining material of a main pipe is attached to a flange of a lateral pipe liming material via a resin-absorbing material. The resin sheet and the resin-absorbing material are thermally welded. The flange and the resin-absorbing material are respectively impregnated with a thermoplastic resin, which is cured to bond the flange and the resin-absorbing material. A similar configuration is provided to the bottom side of the flange as well. The resin sheet of the thermoplastic resin is integrally bonded to the flange, so that the flange of the lateral pipe lining material and the main pipe lining material can be reliably bonded by a simple method through thermally welding of the lining material of the main pipe and the resin sheet, even in a case in which the flange is hard.