PURPOSE: A connection sleeve is provided to prevent the corrosion of a water stop or connection unit by preventing foreign materials or rainwater from contaminating the connection unit. CONSTITUTION: A water stop(110) includes a first disk(111) and a boss(112). The boss is welded at the center of the upper and lower sides of the first disk. A connection unit(120) is combined with the upper and lower sides of the water stop. The connection unit includes a second disk(121) and a hollow tube(122). The hollow tube is welded at the center of the upper and lower sides of the second disk. A conductive cap(130) is combined with the upper and lower ends of the hollow tube.