A first switch for performing both a weight balancing operation for a main parallel linkage and a weight balancing operation for a supplemental parallel linkage is provided separately from a second switch for only performing a weight balancing operation for the supplemental parallel linkage. An operator can press the second switch during surgery to only correct a slightly unbalanced state of the supplemental parallel linkage in a short period of time, resulting in increased operability of the operation microscope. While the first switch is provided on an operating panel at a stand body, the second switch is provided at a lower part of a distal link located above an operating space for the operation microscope. It is thus easy for an operator to press the second switch during surgery.