A method for assembling a cell structure in a metal vessel, including reading information as indicia located on a surface of a compressible material having a cushioning property, the information regarding the thickness and/or bulk density of the compressible material; selecting a cell structure, a metal vessel, and a compressible material which, when assembled as a cell structure housed in a metal vessel, have a proper holding condition based on the read information; assembling the selected cell structure in the selected metal vessel via the selected compressible material, the compressible material being located in a compressed state between an outer periphery of the cell structure and the metal vessel to hold the selected cell structure in the selected metal vessel.