To eliminate rubber burr formation at the time of molding and to make sealing members to be surely integrated with the flexible wiring board, a sealing structure consists of housings to which the flexible wiring board is inserted, and sealing members integrally formed on the flexible wiring board to seal gaps between the housings and the flexible wiring board, the flexible wiring board consists of a base board made of an elastic material, a conductive printed wiring layer formed on the surface of the base board, and a cover film covering the surface of the printed wiring layer, and dummy printed wiring layers are arranged in regions where the sealing members are integrated with the flexible wiring board, so as to make a shape as if the printed wiring layer exists substantially over the entire base board in the width direction.