PURPOSE: To regenerate an existing pipe efficiently and securely, by a method wherein a flexible regenerating pipe is inserted into an existing pipe, thereafter a flange body is bonded to a projected tip of the regenerating pipe, and the flange body is clamped between flanges of existing pipes.

CONSTITUTION: The flexible regenerating pipe 9 is inserted into the existing pipe 1 separated to a unit operating length, from one end of the pipe 1, and is projected to the exterior through an opening at the other end. Then, the flange body 12 is bonded to the projected tip of the regenerating pipe 9. A flanged joint pipe 4 fitted over the existing pipe 1 and a flanged joint pipe 8 fitted over a connecting pipe 5' connected to a separated another existing pipe are brought close to each other, the flange body 12 is tightly clamped between the flanges 10, 11 of the joint pipes 4, 8, and the joint pipes 4, 8 are fixed to the existing pipe 1 and the connecting pipe 5', respectively. Accordingly, the existing pipe can be regenerated efficiently and securely.