A battery module includes a case with at least one face which is opened, a plurality of partition walls fixedly installed at predetermined intervals in the case, and a plurality of unit batteries which are separated from each other with the partition walls therebetween to be inserted into the case. The battery module may include a battery fixing structure which is installed between the case and the unit batteries to fix the unit batteries so as to prevent positional movement of the unit batteries in the case. The battery fixing structure may be a concavo-convex engaging structure including fixing projections and projection receiving portions.