PURPOSE: To flatten the titled tube and reduce bulkiness at a transport, and to bring the tube simply to three dimensions by giving proper restoring force while forming a plural stripe of folds in the axial direction and enabling flattening and reversible changes.

CONSTITUTION: Sections between rollers 1, 2 and 3, 4 at every upper and lower one pair are filled with a fixed quantity of fillers 6 from the nose of a tube 5 under the state in which a space between a pair of the rollers 3, 4 positioned on the lower side is enlarged and the rollers 1, 2 positioned on the upper side are brought into contact by pressure. The section between the rollers 3, 4 being opened is brought into contact by pressure, and fillers 6 are confined completely. Fillers 6 are confined completely because they are positioned at the upper and lower pairs of the rollers brought into contact by pressure, and are sealed in the tube between the upper and lower pairs of the rollers at all times. Since four folds AWD are formed in the obtained square tube 5', stiffness is increased and the state of a square is kept, and a completely opened state is maintained.