A secondary battery includes a can having an interior space, an electrode assembly provided in the interior space of the can, and a cap assembly seated on an opening formed in the can to seal the can and electrically connected to the electrode assembly. The cap assembly includes a cap plate connected to the opening to seal the can; a tab plate mounted to one side of the cap plate and connected to the electrode assembly; an insulating plate interposed between the cap plate and the tab plate; an electrode pin passing through the cap plate, the tab plate, and the insulating plate to interconnect these elements; and an insulating gasket interposed between the cap plate and the electrode pin. Also, the electrode pin includes a head portion mounted to one side of the cap plate and formed in multiple stages in an area contacting the insulating gasket; and a column extending from the head portion and passing through the insulating gasket, the cap plate, the insulating plate, and the cap plate.