A secondary battery includes an electrode assembly, a battery case, and a cap assembly. The electrode assembly includes first and second electrodes. The battery case accommodates the electrode assembly therein and has an opened surface. The cap assembly seals the battery case and includes first and second terminal portions coupled to the respective first and second electrodes. In the secondary battery, at least one of the first and second terminal portions is coupled to a variable member including a plurality of variable plates. Accordingly, the path and resistance of current may be varied in the secondary battery, so that it is possible to reduce or prevent generation of heat caused by overcurrent. Thus, it may be possible to reduce or prevent an explosion and fire of the battery, thereby improving the safety of the battery.