In a master-slave manipulator system capable of presenting an obstacle and a limit to an operating range as a force feed-back with no use of a motor in an operation input device and having high reliability, a small size and good operability, the system comprises a manipulator having an arm, an operation input device for moving the arm of the manipulator, and a controller for controlling the manipulator and the operation input device, and the operation input device is provided on joints with a mode change-over mechanism having three modes: of which, in a first mode, power is not transmitted; in a second mode, power is transmitted in one direction and is not transmitted in a reverse direction thereof; and in a third mode, power is transmitted in the reverse direction and is not transmitted in the one direction, selecting one of the above modes and changing over from one mode to the selected mode.