Abstract: Disclosed is a miniaturized battery module in which a space except for a space of a battery cell is minimized and the number of components is reduced. The miniaturized battery module includes a cell assembly configured by assembling a plurality of battery cells, an upper frame inserted into an outer upper surface of the cell assembly, a lower frame inserted into an outer lower surface of the cell assembly and fastened to the upper frame, and first and second endplates fastened to two opposite ends of the cell assembly and configured to fix the plurality of battery cells. In this case, at least two or more of the plurality of the battery cells are arranged side by side, and the upper frame and the lower frame are fastened by welding.