To form a conductive connection structure having good connection characteristic between a conductive connection tab to which a battery element is connected and a battery can.

In this connection structure of the conductive connection tab of the battery, the conductive connection tab joined to the battery element is joined to the inner wall surface of the battery can or the inner surface of a cover. The conductive connection tab having a plurality of projections for projection welding is brought into contact with the inner wall surface of the battery can or the inner surface of the cover to be joined to each other by projection welding.