A battery module includes a battery cell stack having a plurality of battery cells or unit modules connected in series and/or in parallel to each other in a state in which the battery cells or the unit modules are stacked in the lateral direction. The battery cell stack is provided at the front thereof with bus bars to connect electrode terminals of the battery cells to external input and output terminals. Voltage sensing members are provided at ends thereof with connection terminals electrically connected to electrode terminal connection parts of the battery cells to sense voltages of the battery cells or the unit modules. An upper case is provided with mounting parts, in which the voltage sensing members are mounted. A lower case is coupled to the upper. The lower case is provided at the front thereof with external input and output terminals.