An arm main body moves a distal end portion with respect to the proximal end portion. A translation arm includes a proximal end side link. A distal end side link has a proximal end portion continuous with the proximal end side link distal end portion and pivots about a second axis parallel to a first axis and within a range. A translation arm drive unit causes the proximal end side link and the distal end side link to pivot with the translation arm drive unit driving force, and an instrument holder is continuous with the translation arm distal end portion and to hold a surgical instrument including a long-axis shaft and a treatment tool at the shaft distal end portion in a posture in which the shaft extends in the reference direction.
