Abstract: The present invention is a sealed storage battery wherein a plurality of flattened unitary cells formed by sealing a polar plate group in an outer bag made of a sheet or a film of synthetic resin are stacked in a direction thicknesswise thereof and accommodated in a pressurized manner in a casing.By so constructing, the unitary cells can be uniformly applied with pressure with the increased capacity for efficiency for a battery, any possible deviation in the lifetime of the cells can be eliminated, and a highly reliable battery of flat type easy to fabricate, and suitable for use as an electric power source for portable electric appliances can be obtained.