A watertight slide fastener includes two tapes each having a waterproof layer. Each of the two tapes includes an inner edge on which a plurality of consecutively disposed scoops and an upper stopper scoop made of a rigid plastic are mounted. A first end of each upper stopper scoop is contiguous to the last one of the plurality of scoops. A second end of each upper stopper scoop has an extension. A top end stop is formed on upper and lower faces of each of the two tapes by an elastomer and envelops an upper face and a lower face of each extension. Each of two outer sides of the top end stop has a shoulder. A slider includes an upper body and a lower body interconnected to the upper body by a diamond. Each of two sides of the upper and lower bodies has a flange.