A battery cell includes an electrode assembly mounted in a battery case. The electrode assembly includes positive electrodes, negative electrodes, and separators, wherein the separators are disposed respectively between the positive electrodes and the negative electrodes. The electrode assembly is provided with a deformation part, and has a sectional width of which is discontinuously or continuously decreased, and is formed at a portion of an outer edge of the electrode assembly. The battery case includes two or more case members, each made of a metal sheet, the case members being coupled to each other in a state in which the electrode assembly is mounted in the case members, at least one of the case members having a receiving part with an internal shape corresponding to the deformation part of the electrode assembly.