A battery module comprising: a plurality of secondary battery cells each comprising a housing body including a bottom surface, a pair of main surfaces extending essentially orthogonal to the bottom surface from a pair of long sides of the bottom surface, and a pair of side surfaces extending between the main surfaces, and a lid member opposed to the bottom surface and having electrode terminals (PT, MT); a case (10, 20) for housing the plurality of secondary battery cells; a plurality of conductive members for electrically connecting the electrode terminals (PT, MT) of the secondary battery cells; and a wiring board placed at an upper portion of the conductive members on the case (10, 20), wherein the plurality of secondary battery cells comprises a first cell group including a plurality of secondary battery cells stacked along a first direction, and a second cell group including a plurality of secondary battery cells stacked along a second direction crossing the first direction, the side surfaces of the secondary battery cells of the first cell group are opposed to the main surfaces of the secondary battery cells of the second cell group, and the first cell group and the second cell group are connected in series, and the case (10, 20) includes a first case having a bottom wall opposed to the bottom surface of the plurality of secondary battery cells, side walls including a pair of first side walls (10a, 10b) extending to be opposed to the main surfaces of the secondary battery cells included in the first cell group from edges of the bottom wall, and a pair of second side walls (10c, 10d) extending to be opposed to the main surfaces of the secondary battery cells included in the second cell group from edges of the bottom wall, and a plurality of dividing walls arranged upright to the bottom wall,; characterized by a plurality of concave parts defined by the bottom wall, the first pair of side walls (10a, 10b) and the second side walls (10c, 10d), or the dividing walls, wherein the concave parts support a respective bottom part of the secondary battery cells, and a space in which a component other than the secondary battery cells is placed, the space being enclosed by the dividing walls and the side walls (10a, 10b, 10c, 10d). a plurality of secondary battery cells each comprising a housing body including a bottom surface, a pair of main surfaces extending essentially orthogonal to the bottom surface from a pair of long sides of the bottom surface, and a pair of side surfaces extending between the main surfaces, and a lid member opposed to the bottom surface and having electrode terminals (PT, MT); a case (10, 20) for housing the plurality of secondary battery cells; a plurality of conductive members for electrically connecting the electrode terminals (PT, MT) of the secondary battery cells; and a wiring board placed at an upper portion of the conductive members on the case (10, 20), wherein the plurality of secondary battery cells comprises a first cell group including a plurality of secondary battery cells stacked along a first direction, and a second cell group including a plurality of secondary battery cells stacked along a second direction crossing the first direction, the side surfaces of the secondary battery cells of the first cell group are opposed to the main surfaces of the secondary battery cells of the second cell group, and the first cell group and the second cell group are connected in series, and