A battery module includes first and second plates opposite each other, first and second frames respectively connecting tops and bottoms of the first and second plates to define a casing, the first frame being connected to the second frame and having a shape corresponding to the second frame, and a plurality of battery cells stacked in the casing, each battery cell including a first surface with a terminal portion, the first surface of each battery cell facing the first plate, a second surface opposite the first surface, and a pair of third surfaces spaced part from each other, each third surface connecting the first and second surfaces and being parallel to the second frame.