A coupling member includes a sliding member and a sleeve. The sliding member has one axial direction end portion coupled to a first attachment portion provided at a first attachment that is mounted to one of a maxilla or a mandible. The sleeve has one axial direction end portion coupled to a second attachment portion provided at a second attachment that is mounted to the other of the maxilla and the mandible. The sliding member is inserted into the sleeve so as to be slidable. A restricting section is formed at the sleeve between two axial direction end portions of the sleeve so as to restrict sliding of the sliding member in both directions along an axial direction of the sliding member.