A rechargeable battery includes an electrode assembly that performs charging and discharging operations, a case that accommodates the electrode assembly therein, a cap plate coupled to the case, an electrode terminal connected to the electrode assembly and mounted in a terminal hole of the cap plate, and an insulation member that coats the case. The insulation member has a protruding portion that protrudes from an external circumference of the cap plate along a surface of the cap plate. The protruding portion has an exhaust groove on at least one side thereof.