To widen the connecting area of a terminal.

An upper aperture of a battery container 10 is caulked with a seal lid 12 through a gasket 11. An annular projecting part 16 is formed inside a flat part 15 having a constant width from the peripheral edge of a seal plate 13, and an elastic valve element 19 is contained in the central recessed part 17. And, a flat platy positive electrode terminal plate 14 is put on the upper aperture.