PURPOSE: To increase the preservation life of an air cell without using any sealing member by using an exterior can obtained by forming an oxygen-gas permselective film on the surface of a porous structure.

CONSTITUTION: An exterior can 8 is obtained by forming an oxygen-gas permselective film 8" consisting of a specified metal oxide or metal on the surface of a porous structure 8' made of metal, ceramics, organic matter or the like by sputtering or vapor deposition. The film 8" has a thickness of 0.01∼1μm and formed by sputtering, vapor deposition or similar method by use of, for example, either at least one hydrous metal oxide selected from among tin oxide, zinc oxide, aluminum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide and silicon oxide or a metal such as Sn, Ni or Cr.