Abstract: A double-layer water-proof zipper in which the slide has an additional second interlocking unit moved with the slide to close a water-proof layer so as not to let rain pass through the interlocked teeth of the zipper tape unit of the zipper. The water-proof layer includes two water-proof tapes, the water-proof tapes each having two longitudinally extended parallel grooves and two longitudinally extended protruding portions respectively raised along said parallel grooves at one side for interlocking.