In arm support apparatus, a longitudinal mount has opposing first and second ends. An elbow locator is provided on the first end of the mount. The elbow locator locates an operators elbow when the operators forearm is mounted on the mount. A rotary joint of a multijoint arm has a rotary axis having a vertical component. The mount is rotatably joined to the rotary joint. While the forearm is mounted on the mount so that the elbow of the operators arm is located by the elbow locator, the rotary axis is located with a distance with respect to the elbow to enable both the first and second ends of the mount to swing about the rotary axis. The distance is set to be equal to or longer than 50 mm.
