A water-stop structure including a water-stop tube is provided in which the water-stop tube can be brought into intimate contact with a water-stop region in a wire harness having a steep thickness gradient and thus water-stop performance is improved. The wire harness includes a first portion and a second portion that is thinner than the first portion. An inner water-stop tube covers the water-stop region ranging from the first portion to the second portion in a state where the inner water-stop tube is heated and shrunk. An outer water-stop tube covers the inner water-stop tube at a position between a portion on the first portion side and a portion on the second portion side in the water-stop region in a state where the outer water-stop tube is heated and shrunk.