A middle- or large-sized battery module includes two or more unit modules each having one or more plate-shaped battery cells, as unit cells, surrounded by a high-strength sheathing member made of synthetic resin or metal, and separable upper and lower frame members coupled with each other in an assembly-type coupling structure such that the unit modules are vertically mounted in the upper and lower frame members. A sensing unit capable of minimizing the weight and size of battery cells is easily mounted while effectively reinforcing the low mechanical strength of the battery cells and sensing the operation state of the battery cells to a middle- or large-sized battery module. The battery module is manufactured by a simple assembly process without using a plurality of members for mechanical coupling and electrical connection.