A water stop sheet to be wound around a wiring harness wired in a vehicle includes a closed-cell elastic sheet, an entire adhesive layer provided on one surface of the elastic sheet, and a partial adhesive layer provided only on a part of the other surface along one end edge. The water stop sheet is wound with the entire adhesive layer located on an inner surface side to be held in contact with the outer periphery of a wire group of the wiring harness and wound at least one turn. A winding end part is placed on the outer peripheral surface of a winding start part. The partial adhesive layer located on the outer peripheral surface of the winding start part and the entire adhesive layer located on the inner peripheral surface of the winding end part are adhered to each other.