Disclosed herein is a middle- or large-sized battery module including 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 mountedin the upper and lower frame members. The present invention has the effect of easily mounting a sensing unit that is capable of minimizing the weight and size of battery cells 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. In addition, the present invention has the effect of manufacturing the battery module by a simple assembly process without using a plurality of members for mechanical coupling and electrical connection, thereby decreasing the manufacturing costs of the battery module, and effectively preventing the battery module from being short-circuited or damaged during the manufacture or the operation of the battery module. Furthermore, the present invention has the effect of manufacturing a middle- or large-sized battery system having desired output and capacity using the battery module as a unit body.