Disclosed herein are a secondary battery, which is formed in the shape of a plate and has an electrode assembly mounted in a battery case made of a laminated sheet including a metal layer and a resin layer, wherein the secondary battery is constructed in a structure in which independent coupling type frame members are mounted to the outside part of a sheathing member serving as the battery case, and a medium- or large-sized battery module including the same as a unit cell. Consequently, the secondary battery has a high mechanical strength and a large sealing force. Furthermore, the electrical connection is accomplished without bending the electrode leads. Also, the battery module, which is constructed with the secondary battery as a unit cell, can be manufactured with a compact structure and a relatively light weight. Furthermore, the assembly process of the battery module is greatly simplified. The structural stability of the battery module according to the present invention is very high, and therefore, the battery module can be preferably used as a power source for electric vehicles, hybrid electric vehicles, electric motor cycles, and electric bicycles.