In a robot for training a rehabilitator, the driving of actuators is controlled to generate the forces acting in six directions at the distal end of a bi-articular arm device to reproduce the relationship between the muscular output of the upper or lower limb of the human body and the output direction at the distal end of the limb. The rehabilitator can experience the relationship between the outputs of his or her limb muscles and the output direction at the distal end of the limb. Thus, the six actuators are run in operation along a predetermined sequence. One or more of the actuators, selected so that the direction of the force generated at the distal end of the first link will be the selected direction, is run in operation. The rehabilitator holding the distal end of the first link may physically experience the direction of that force.