To improve a bag unbreakable characteristic of a shrink tube having a cutting line while keeping a superior cutting characteristic of the cutting line.

This cutting line (1) is comprised of a row of small perforations (2) having a thick walled hole edge (21). The perforations in a surface area A facing a constriction (23) of a container have a smaller hole diameter (d2) or a larger hole pitch (p2) as compared with that of perforations in a surface area (a surface area other than A) except an outer surface area. At a stage for heat shrinkage processing for installing this tube to the container, although the surface area A produces a large heat shrinkage deformation, it may produce a reinforcement and strength because the hole edge (21) of each of the small perforations (2) has a thick wall; a high unbreakableness as an effect of adjustment of the hole pitch (p2); and a neat installed finish state without producing any breakage of the tube. The cutting line (1) can be formed efficiently through a laser beam radiation work.