The invention relates to an apparatus for robot-assisted surgery, a positioning device (600, 700) as well as a method for assisting in the positioning of a manipulator arm (16) of an apparatus for robot-assisted surgery. The apparatus comprises a positioning device (600, 700) which is connected to a coupling unit (100) of the manipulator arm (16) instead of an instrument unit (300). The instrument unit (300) has a surgical instrument (500) with an instrument shaft (512), the proximal end (514) of which is passable through a body orifice of a patient (18) to a target area (30).
