Proposed is a mechanism capable of securing both convenience and safety in regard to surgery performed by inserting an endoscope into a human body.A medical arm system including: a multi-joint arm which has a plurality of links connected by joints and a distal end to which an endoscope is connectable； and a control unit which sets a virtual plane in a body cavity of a patient and controls the multi-joint arm so as to constrain a predetermined point of the endoscope in the body cavity on the virtual plane.
