A joint structure includes a rotating guide pulley, a fixed guide, and a rotating guide pulley. The rotating guide pulley is coaxial with a rotating shaft of a revolute joint, and is arranged so as to be rotatable about the rotating shaft. The fixed guide is arranged in a first structure, and has an arc portion. The arc portion has the same radius as the rotating guide pulley and is coaxial with the rotating guide pulley. The rotating guide pulley is arranged in a second structure so as to be relatively movable. A wire is put round the rotating guide pulley, the movable rotating guide pulley, and the fixed guide in the order of them.