A medical observation device comprising: an imaging unit configured to capture an image of an operation site comprising an observation point; a holding unit connected with the imaging unit and configured to have six rotary shafts (O1, O2, O3, O4, O5, O6) which are operable to provide the imaging unit with six degrees of freedom, wherein, among the six rotary shafts, at least three of the rotary shafts are active shafts (O2, O3, O4) whose rotation is caused by an actuator (223, 233, 643) of each of the three active rotary shafts controlled by a controller based on a rotation angle detected by an encoder (212, 222, 232, 642, 252, 262) of each of the six rotary shafts, and the remaining rotary shafts (O1, O5, O6) are passive shafts which are rotated according to direct external manipulation by a user, wherein the active shafts include a first rotary shaft which is orthogonal to an optical axis of the imaging unit and a second rotary shaft orthogonal to the first rotary shaft, and the passive shafts include a third rotary shaft substantially coinciding with the optical axis; wherein a rotation of the first rotary shaft is configured to adjust a tilt of the imaging unit in the direction of the second rotary shaft; wherein a rotation of the second rotary shaft is configured to adjust a tilt of the imaging unit in the direction of the first rotary shaft; characterized in that the active shafts further include a fourth rotary shaft corresponding to a parallelogrammic link mechanism which can adjust a translation of the imaging unit along a z axis direction to decide a distance between the imaging unit and the observation point, and when the imaging unit is moved via any of the shafts, driving of the active shafts is controlled by the controller such that: the observation point remains positioned on the optical axis of the imaging unit so that the observation point with respect to the imaging unit after movement coincides with the observation point with respect to the imaging unit before movement, and such that a distance between the imaging unit and the observation point is maintained to be constant. an imaging unit configured to capture an image of an operation site comprising an observation point; a holding unit connected with the imaging unit and configured to have six rotary shafts (O1, O2, O3, O4, O5, O6) which are operable to provide the imaging unit with six degrees of freedom, wherein, among the six rotary shafts, at least three of the rotary shafts are active shafts (O2, O3, O4) whose rotation is caused by an actuator (223, 233, 643) of each of the three active rotary shafts controlled by a controller based on a rotation angle detected by an encoder (212, 222, 232, 642, 252, 262) of each of the six rotary shafts, and the remaining rotary shafts (O1, O5, O6) are passive shafts which are rotated according to direct external manipulation by a user, wherein the active shafts include a first rotary shaft which is orthogonal to an optical axis of the imaging unit and a second rotary shaft orthogonal to the first rotary shaft, and the passive shafts include a third rotary shaft substantially coinciding with the optical axis; wherein a rotation of the first rotary shaft is configured to adjust a tilt of the imaging unit in the direction of the second rotary shaft; wherein a rotation of the second rotary shaft is configured to adjust a tilt of the imaging unit in the direction of the first rotary shaft; characterized in that the active shafts further include a fourth rotary shaft corresponding to a parallelogrammic link mechanism which can adjust a translation of the imaging unit along a z axis direction to decide a distance between the imaging unit and the observation point, and when the imaging unit is moved via any of the shafts, driving of the active shafts is controlled by the controller such that: the observation point remains positioned on the optical axis of the imaging unit so that the observation point with respect to the imaging unit after movement coincides with the observation point with respect to the imaging unit before movement, and such that a distance between the imaging unit and the observation point is maintained to be constant.