PURPOSE: To accurately reproduce the position data of a three-dimensionally caught lesion in actual operation and to simplify operation searching the optimum craniotomic position by a method wherein a reference point to which a positioning implement is directed is allowed to coincide with a revolving axis and the position of the reference point is made freely detectable by a position detection means.

CONSTITUTION: In order to move the focus (f) of an operating microscope 5 to the lesion T within the head E from the position of the origin G, the whole of a parallel link unit 4 is again moved by a support unit 9 on the basis of the three-dimensional coordinates (x, y, z) of the lesion T obtained from CT or MRI. That is, electromagnetic clutches C1-C3 are made free and the whole of the parallel link unit 4 is moved by the support unit 9 until all of the three-dimensional numerical values showing the present position of the focus (f) displayed on the monitor picture of a computer coincide with the previous coordinates position (x, y, z) showing the position of the lesion T obtained from the CT or MRI. Once the Coordinates numerical values coincide with the coordinates position, the operating microscope is always directed to the lesion T [focus (f)] and, therefore, when the visual field part thereof is subjected to craniotomy, the operating microscope necessarily reaches the lesion T.