A pipe lining material for lining the main pipe of a sewer has a soft tubular resin absorption material impregnated with a liquid thermosetting resin, and also has a biodegradable film applied to the external peripheral surface of the pipe lining material. The pipe lining material is everted and inserted in the main pipe, pressed against the internal peripheral surface thereof, and cured to line the main pipe. After the lining is complete, there is no need to peel away and dispose of the biodegradable film because the film that is left behind is naturally decomposed and removed by microorganisms residing within the main pipe. This allows lining work to be simplified and carried out in a shorter period of time, reduces operation costs, and improves the lining finish.