In order to solve a technical problem according to the present disclosure, provided is a cylindrical secondary battery capable of preventing the deformation of components during the manufacture or use thereof. To this end, the present disclosure provides a cylindrical secondary battery comprising: a cylindrical can; an electrode assembly accommodated in the cylindrical can; and a cap assembly for sealing the electrode assembly by covering the cylindrical can, wherein the cap assembly includes: a cap-up portion; a cap-down portion provided below the cap-up portion; and a safety vent provided between the cap-up portion and the cap-down portion, and the elongation rates of the cap-down portion and the safety vent are different from each other.