To provide a branch pipe lining construction method which allows no burrs to remain in a branch pipe lining material, or no pinholes to be formed in the resin film of the branch pipe lining material, and facilitates operation because a pressure bag is not coupled to the branch pipe lining material.

The branch pipe lining material 1 constituted by impregnating a flexible tube 2 having a flange 3 in its one end with a hardnable resin is stored in the pressure bag 5 whose base end is closed from another end to a flange 3 side. The front end side folded and extended outward near the flange 3 is closed to make the space within the pressure bag 5 a sealed space, a fluid is compressed and supplied into the sealed space 6 from a fluid supply tube with the flange 3 of the branch pipe lining material 1 pushed and pressed to the opening fringe 52A of a branch pipe, the branch pipe lining material 1 moves into the branch pipe 52 while reversing it to bring the same to pressed contact with the inner wall 52B of the branch pipe by the expanding pressure of the pressure bag 5, and the hardnable resin of the branch pipe lining material 1 is cured in this state.