A relatively large rectangular sealed alkaline storage battery used for electric cars, etc. is disclosed. The battery has such an inner construction as to inhibit deformation of the electrode group caused by charging and discharging so as to improve the life characteristics. The electrode group comprises positive electrode plates alternating with negative electrode plates in a planar direction and separators between the adjacent electrode plates. The electrode group and an alkali electrolyte are inserted in a container, which is sealed by a cover provided with a safety vent and the position of the electrode group in the container is controlled by fixing poles to the cover. The amount of the alkali electrolyte is 1.5-2.5 cm3/battery capacity 1 Ah. Especially, for a module battery, a given distance is provided between the shorter side face of the electrode group and the inner wall of the container, and the outer longer side faces of the container are constrained by a metallic plate.