Manufacturing method of battery

This manufacturing method of batteries that comprises the steps of accommodating a battery element 4 in an envelope film body 3 of which one end side is opened to form an opening 3a for injecting an electrolytic solution; and sealing the opening 3a after the electrolytic solution 12 is injected from the opening 3a of the envelope film body 3; wherein an opening 3a side of the envelope film body 3 is made larger than a prescribed shape and dimension to use as a temporary reservoir region 3c of an injected electrolytic solution 12, after injection of a prescribed amount of the electrolytic solution 12 the region 3d of the prescribed shape and dimension being sealed and cut to form a battery. According to the method, a manufacturing method of batteries that can not only make smaller and lighter the batteries but also mass-produce batteries of high quality can be provided.