PURPOSE: To obtain a cylindrical air cell with the excellent mechanical strength for the external force applied to both upper and lower terminal blocks by biting an armored can made of metal into the upper and lower gaskets and providing a recessed groove.

CONSTITUTION: Recessed grooves 13 and 14 having a depth where an armored can 10 advances into upper and lower gaskets 3 and 4 are provided at a location where the armored can 10 and upper gasket 3 and the armored can 10 and lower gasket 4 are made adhere to each other, respectively. The shape of the recessed grooves 13 and 14, number of both grooves, their width, and depth are especially restricted. In addition, the recesses can externally be provided on all surfaces of the location or be arranged discontinuously at the proper position of the location, but normally it is recommended that they should be a single continuous semicircular recessed groove. As a result, the mechanical strength for the external force in the vertical direction of a cylindrical air cell can be improved and the faulty condition of the cell can be prevented.