A joint mechanism 4 has a zigzag structure 13 extending in a zigzag pattern between a first member 11 and a second member 12. A flexible lengthy member 16 fixed to the first member 11 extends from the first member 11 toward the second member 12 and is travelable with respect to the second member 12. A tension application unit 30 that applies a tension to the flexible lengthy member 16 is configured to be capable of changing a tension to apply.
