To provide a light-weight sheath-can capable of efficiently preventing the deformation such as bulging of the sheath-can without increasing the outer dimension of a battery and enhance battery characteristics by forming with an Al alloy and increasing the thickness in the straight part of the major axis than that in the strength part of the minor axis.

A sheath-can of a square battery is molded with an Al alloy, the thickness 21t in the straight part of the major axis 21 is more increased than the thickness 22t in the minor axis 22. By having this shape and molding with the Al alloy, in a secondary battery, the material saving of the can is maximized, weight is lightened, and a battery having a high weight-energy efficiency can be obtained. The top of the can is finally sealed with a sealing body or by a means of laser welding. The thickness 22t in the straight part of the minor axis 22 to be the thinnest part, is needed to be at least 0.1 mm which is the minimum thickness for welding, and since the minimum thickness for press molding is 0.2 mm, the thickness 22t is made 0.2 mm or more.