To provide a method of manufacturing a resin connecting tube which can improve bonding strength and thus, can improve product quality in a manufacturing technology for resin connecting tubes formed by interconnecting opening ends of resin tubes, and the resin connecting tube.

The method of manufacturing the resin connecting tube includes: a flange forming process of forming a first flange 23 at an opening end 21 of a first resin tube 20 and forming a second flange 53 at an opening end 51 of a second resin tube 50; and a welding process of forming a welded part 60 by welding the first flange 23 of the first resin tube 20 and the second flange 53 of the second resin tube 50 to each other in such a state that the first and second flanges 23, 53 abut on each other.