To provide a connection structure of double layer pipes, etc., which can be easily connected, which is excellent in light resistance (weatherability), and which is low cost in connecting cost and material cost.

Pipes 3a, 3b are double layer pipes constituted of inner layers 7 and outer layers 9. The inner layers 7 and the outer layers 9 are made of resin for example polyethylene. Carbon black is mixed to the outer layers 9 in older to enhance light resistance. The thickness of the outer layers 9 is greater than that of the inner layers 7. That is, in the case of envisioning the center line of the wall thickness the pipes 3a, 3b, the center line is formed in the outer layer 9 sides. When performing butt fusion, the outer peripheral bead 5a is formed in the outer surface part of the connection part of the pipes 3a, 3b. The end surfaces of the pipes 3a, 3b are softened by heating them, the ends of the pipes 3a, 3b are deformed by abutting the ends by applying pressure to them, thereby the outer peripheral bead 5a is formed. The outer peripheral bead 5a is formed of the resin constituting the outer layers 9.