A rechargeable battery module includes unit cells that are arranged in a first direction, a bus bar that electrically connects the unit cells, a pair of end plates that are spaced apart from each other along the first direction at opposite ends of the unit cells to support the unit cells, and at least one side plate between the pair of end plates and connected to the pair of end plates, the at least one side plate extending along the unit cells and spaced apart from the unit cells a predetermined distance, wherein the side plate includes a stepped portion facing the unit cells.