The invention has for its object to provide a manipulator system that has no or little influences on the surroundings even when a treatment tool is engaged with a drive unit after the insertion of the treatment tool through the body cavity, thereby allowing for unerring engagement of the treatment tool with the drive unit. The manipulator system 1 includes a treatment tool 3, a first engagement portion 41a attached to the treatment tool 3 and formed on each of first driving force transmission members 41 to which associated driving forces are transmitted from a plurality of driving members 21, and a second engagement portion 42a formed on each of a plurality of second driving force transmission members 42 for transmission of associated driving forces to the plurality of first driving force transmission members 41. Mounting and demounting of the first on and out of the second engagement portions are separately sensed by an engagement sensor unit, and when the engagement of the first 41a with the second engagement portion 42a is sensed, there is deactivation of the second driving force transmission member 42 of the plurality of second driving force transmission members 42, which member has the sensed engagement portion 42a.
