There is provided a secondary battery in which a gasket is melted by internal heat generation to prevent the secondary battery from being short circuited to each other. In one embodiment, a secondary battery includes an electrode assembly having a positive electrode plate, a negative electrode plate and a separator interposed between the positive and negative electrode plates. A can accommodates the electrode assembly and is connected to the negative electrode plate through negative electrode tabs. A cap assembly is positioned at one side of the can and electrically connected to the positive electrode plate through a positive electrode tab. A gasket is positioned between the can and the cap assembly. In the secondary battery, the gasket is formed of a heat resistant material having a predetermined amount of heat-resistant enhancing material added thereto.