To simplify a current breaking mechanism which is connected with a battery and installed on a connecting plate electrically continuous with an external apparatus.

A connecting plate 4 consists of a first connecting plate 7 which is arranged so as to almost be in contact with a battery 3, and a second connecting plate 8 which is arranged so as to overlap with the first connecting plate. A contact point 8a, which protrudes in an intermediate part of the part where both of the connecting plates 7, 8 overlap, is arranged on the second connecting plate 8. The first connecting plate 7 and the second connecting plate 8 are bonded at the contact point 8a by a specified bonding force. Insulating layers 9 are arranged on both sides of the contact point 8a, so as to be interposed between both of the connecting plates 7, 8. The insulating layers 9 are constituted of adhesive tapes containing foaming layers which expands at a specified temperature. Separating force of both of the connecting plates 7, 8 which is caused by increase in the thickness caused by the expanding of the foaming layers is made greater than the specified bonding force.