Disclosed herein is a battery module including two battery cells, each of which has electrode terminals formed at upper and lower ends thereof. The battery module further includes a frame member, to which upper-end sealing parts, lower-end sealing parts, and one-side sealing parts of the battery cells are mounted, a metal sheathing member for covering the outer surfaces of the battery cells while the battery cells are mounted to the frame member, and caps (an upper-end cap and a lower-end cap) mounted to the upper and lower ends of the battery cells, respectively, which are covered by the metal sheathing member. According to the present invention, it is possible to minimize the weight and the size of the battery module while increasing the strength of the battery cells. Also, it is possible to easily mount the detecting means that detects the operation of the battery cells, and it is possible to effectively prevent the occurrence of short circuits during the assembly or the operation of the battery module. Furthermore, it is possible to easily perform the electric connection between the battery modules when manufacturing the medium- or large-sized battery module using the respective battery modules as unit bodies.