PURPOSE: To maintain rotating accuracy of a drum by enhancing flowing uniformity of treating medium on the surface of a material to be treated which is carried along the overcoat of a drum and preventing concave-convex deformation of a drum face caused by negative pressure.

CONSTITUTION: In a sheave drum for processing textile material, fleece, paper or the like, a drum overcoat 5 which receives aspirating force is composed of a perforated thin plate and an inside edge in a radius direction of an underlaying body which comprises a thin plate belt-like material 10 having a rectangular, square or circular cross section and is extended in the whole length of the drum overcoat 5 is formed on the outer periphery of the drum overcoat 5 by forming a welding joint 13 by a method such as a spot welding between the dram overcoat and a streak-shaped coated material 9 covering the outer periphery of the thin plate and immovably fixed t to the drum overcoat so as to maintain the rigidity of the carrier element. Further a web 14 is arranged between thin plate belt-like materials 10 and a part of the whole drum length is covered with a side cover. The flow of a gaseous or liquid treating medium passing a part of the drum overcoat 5 coated with the cover when operation width is adjusted is prevented so as to make the treating medium uniformly pass the material to be treated.