A rechargeable battery and rechargeable battery module, the rechargeable battery including a case housing an electrode assembly, a cap plate sealing the case, at least one first insulator disposed on an outer surface of the cap plate, a pair of electrode terminals penetrating the cap plate and the first insulator, and a bus bar coupled to one of the electrode terminals, wherein the cap plate and first insulator include a first joining unit coupling the first insulator and the cap plate and the first insulator and bus bar include a second joining unit selectively coupling the first insulator and the bus bar.