Disclosed herein is a battery module using battery cells each having an electrode assembly mounted in a battery case including a resin layer and a metal layer as unit cells, wherein each battery cell has a thin upper end, including a sealing part, which is formed at a region where electrode terminals are placed, and an impact- absorbing member is mounted at the upper end of each battery cell. Thebattery module according to the present invention prevents the weak upper parts of battery cells, such as electrode terminals and sealing parts, from the breakage of the battery module or the occurrence of a short circuit in the battery module due to the movement of the battery cells caused by dropping of the battery module or application of external impacts to the battery module. Furthermore, the battery module according to the present invention is constructed in a structure in which the battery module can be flexibly extended and contracted depending upon desired electrical capacity and output, wires used to electrically connect components constituting the battery module are compact, and the electrical connection between the components of the battery module is stably accomplished.