PURPOSE: To perfectly apply the lining of a tubular lining material even to the bent part of a pipeline so as to almost coincide with the shape of the bent part of a worn-out pipe without generating wrinkles in said lining material even inside the bent part, by cutting the part corresponding to the bent part of the worn-out pipe if the lining material into a predetermined shape to remove the same and bonding the cut parts each other.

CONSTITUTION: The areas (a), (b) of the part 2a corresponding to the bent part 1a of a worn-out pipe 1 of a tubular lining material 2 are cut into a predetermined shape to be removed. The cut and removed parts (a), (b) are equilateral triangles wherein vertical angles B, C' are 45°. When cut lines BF, BG' and cut lines C'H', C'I' are respectively bonded, the part 2a is made approximate in its shape in a polygon AEFHJDCB of a bending angle of 90° with respect to the shape of the bent part 1a of the worn-out pipe 1 having a radius of curvature (r). The lining material 2 is reversed to be inserted in the pipe 1 and water is injected from a hose 3. When reversal insertion reaches the bent part 1a of the pipe, the thermosetting resin infiltrated in the lining material 2 is cured to apply perfect lining generating no wrinkle.