PROBLEM TO BE SOLVED: To provide a joint driver which is capable of responding to a change in position and the attitude of a momentary rotation shaft of a joint by a lightweight, small and simple mechanism.SOLUTION: A joint driver 10 includes a rotation driving mechanism 11 attached to a first region of a human body on one side with respect to a joint, a first link member 12 attached to the rotation driving mechanism and rotated by the rotation driving mechanism, a second link member 13 having a first connecting member 15 with a sliding mechanism, passively slidably connected along the first link member in a state perpendicular to the first link member by the first connecting member, a holding member 14 holding a second region of the human body on the other side with respect to the joint, and having a second connecting member 16 with a sliding mechanism, and passively slidably connected along a second link member by a second connecting member. In accordance with the rotation of the rotation driving mechanism, the first connecting member and the second connecting member passively slide, and rotates the second region around the joint with respect to the first region.
