The present invention relates to an active positioning device for a surgical instrument arranged on a robot arm, comprising a carrier plate (3, 33), which can be connected with a robot arm (1, 31), a port mechanism (4, 34), which is arranged on carrier plate (3, 33) and intended as entry point into the interior of a body, at least one guide device (6, 36, 59) for insertion of a surgical instrument (8, 38, 61) into the body, whereby the shaft of surgical (8, 38, 61) instrument extends through guide device (6, 36, 59) and whereby guide device (6, 36, 59) is variably connected to port mechanism (4, 34) via a compensating element (5, 35) and an adjustment device (9, 10, 11, 12, 13, 14, 39, 40, 41, 42, 43, 44, 62, 63, 64, 65, 66, 67) for guide device (6, 36, 59) opposite port mechanism (4, 34), which is arranged on carrier plate (3, 33) and/or port mechanism (4, 34) on the one hand and guide device (6, 36, 59) on the other hand, in such a way that the shaft of surgical instrument (8, 38, 61) is movable both in x-direction and y-direction in relation to the starting position, in which the longitudinal extension of the surgical instrument runs parallel to the longitudinal extension of port mechanism (4, 34).
