Provided is a surgical apparatus for an endoscope that can appropriately and easily perform mounting work of an endoscope onto an outer tube. An outer tube 300, which passes through a body wall, is inserted into a body cavity, and guides an endoscope and a treatment tool into the body cavity, includes a slider 400 that is an interlocking member that moves the endoscope and the treatment tool forward and backward in an interlocking manner. At the time of mounting of an endoscope in which an endoscope insertion part 102 is coupled to a slider body 402 of the slider 400, the endoscope insertion part 102 is inserted to a position where a larger-diameter part 140 provided in the endoscope insertion part 102 abuts against a base end surface 302 of an outer tube 300. Accordingly, the slider body 402 can be coupled to a predetermined suitable position of the endoscope insertion part 102.
