A cylindrical battery having a sealing unit which includes at least a valve member, a metal plate disposed farther inside the battery than the valve member and having a joint portion connected to the valve member, and an annular insulating member disposed between an outer peripheral portion of the valve member and an outer peripheral portion of the metal plate. The metal plate has a groove-shaped thin portion disposed around the joint portion, and straight portions that have different angles to the normal to the metal plate are disposed on an inner peripheral side and an outer peripheral side of a cross section of the thin portion perpendicular to the longitudinal direction.