Provided is a waterproof structure for a multicore wire capable of enhancing waterproofness. The waterproof structure includes a multicore wire in which a plurality of core wires are housed in a sheath, a housing in which is housed a terminal fitting connected to a terminal portion of the core wires, and in which is formed an opening through which the core wires are externally extracted, a molded part covering the opening and covering an end face of the sheath, and a resin stopper part disposed on an inner side of the molded part inside the opening.