A secondary battery comprising: a cylindrical can having an upper end opening; an electrode assembly received in the cylindrical can and having an electrode tab (124, 125); and a cap assembly for sealing the upper end opening of the cylindrical can, wherein the cap assembly includes: a circular-plate-shaped safety plate; and a cap-up disposed on the upper portion of the safety plate and surrounding the edge portion of the safety plate, and the electrode tab (124, 125) is in contact with and coupled to the cap-up, characterised in that the cap-up comprises: a terminal portion in the shape of a flat circular plate; a connection portion that is bent downwardly from an edge of the terminal portion; a first extension portion that extends outwardly from a lower end of the connection portion in the horizontal direction; a bent portion that is bent downwardly from an edge of the first extension portion; and a second extension portion that extends inwardly from a lower end of the bent portion in the horizontal direction. a cylindrical can having an upper end opening; an electrode assembly received in the cylindrical can and having an electrode tab (124, 125); and a cap assembly for sealing the upper end opening of the cylindrical can, wherein the cap assembly includes: a circular-plate-shaped safety plate; and a cap-up disposed on the upper portion of the safety plate and surrounding the edge portion of the safety plate, and the electrode tab (124, 125) is in contact with and coupled to the cap-up, characterised in that the cap-up comprises: a terminal portion in the shape of a flat circular plate; a connection portion that is bent downwardly from an edge of the terminal portion; a first extension portion that extends outwardly from a lower end of the connection portion in the horizontal direction; a bent portion that is bent downwardly from an edge of the first extension portion; and a second extension portion that extends inwardly from a lower end of the bent portion in the horizontal direction. a circular-plate-shaped safety plate; and a cap-up disposed on the upper portion of the safety plate and surrounding the edge portion of the safety plate, and the electrode tab (124, 125) is in contact with and coupled to the cap-up, characterised in that the cap-up comprises: a terminal portion in the shape of a flat circular plate; a connection portion that is bent downwardly from an edge of the terminal portion; a first extension portion that extends outwardly from a lower end of the connection portion in the horizontal direction; a bent portion that is bent downwardly from an edge of the first extension portion; and a second extension portion that extends inwardly from a lower end of the bent portion in the horizontal direction. a terminal portion in the shape of a flat circular plate; a connection portion that is bent downwardly from an edge of the terminal portion; a first extension portion that extends outwardly from a lower end of the connection portion in the horizontal direction; a bent portion that is bent downwardly from an edge of the first extension portion; and a second extension portion that extends inwardly from a lower end of the bent portion in the horizontal direction.