A secondary battery comprising an electrode assembly comprising a first electrode plate, a second electrode plate, and a separator between the first electrode plate and the second electrode plate, a protection film coupled to one end of the electrode assembly, a can accommodating the electrode assembly, and a cap plate coupled to the can, wherein the separator protrudes more toward the protection film than the first electrode plate and the second electrode plate at the one end of the electrode assembly, and wherein the protection film is thermally bonded to an end portion of the separator.