A rechargeable battery includes a case having an opening and accommodating an electrode assembly therein; a cap plate closing and sealing the opening; and a welding bead part along a circumference of the cap plate and at a contact surface of the case and the cap plate, wherein the welding bead part includes first and second regions on a cross-section vertical to a welding progressing direction of the welding bead part, the first region has a first boundary line on the cross-section, a contact surface is between end parts of the first boundary line, the second region has a second boundary line on the cross-section, the first region is between end parts of the second boundary line to form first and second contact points in contact with the first boundary line, the first region is deeper than the second region, and the second region is wider than the first region.