An articulated arm having a first arm member and a second arm member flexibly coupled mutually by a ball joint. From a plurality of through-holes provided in the first arm member 2 to a plurality of holding holes provided in the second arm member, compression coil springs 8 are inserted. Support shafts are inserted, movably back and forth freely, in the through-holes behind the rear end portion of the compression coil springs. A certain support shaft is moved forward by actuator or the like to push the compression coil spring while other support shaft are moved backward. As a result, the second arm member can be moved to a specified position by the ball joint. Stopping state of the second arm member at the specified position is maintained by the balance of position of support shaft and repulsive force of compression coil spring.