Disclosed is a battery pack provided with a plurality of batteries (12) and a pack case (13) in which the plurality of batteries (12) are sealed. A set of electrodes, comprising a positive plate and a negative plate wound or layered around a porous insulating layer, is contained along with an electrolyte solution in a battery case (11), and the opening of the battery case (11) is sealed by a sealing plate. A first internal lead (6), which is electrically connected to either the positive plate or the negative plate, is connected to the inside bottom part of the battery case (11). A second internal lead, which is electrically connected to the other electrode plate, is connected to the sealing plate. The first internal lead (6) is disposed up against the inner surface of the battery case (11). The plurality of batteries (12) are disposed in the pack case (13) such that an area on the outer surface of each battery case (11) corresponding to the first internal lead (6) of that battery faces an inner surface of the pack case (13).