The present invention relates to a battery module. The battery module is characterized by having a structure that comprises: (a) a unit cell assembly in which two or more battery cells or unit modules are connected to each other in parallel or in series; (b) a left case coupled to a left surface of the unit cell assembly and having a first coupling groove extending parallel to a lengthwise direction of the battery module on a left outer surface thereof so that a sensing assembly is coupled and second coupling grooves are respectively formed parallel to a height direction of the battery module in both ends thereof; and (c) a right case coupled to a right surface of the unit cell assembly and having external input/output terminals on a front surface of the battery module arranged opposite each other, the right case having a plurality of fixing grooves in a right inner surface thereof in a direction parallel to a lengthwise direction of the unit cell assembly such that the unit cell assemblies are coupled and fixed.