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, 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 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 is coupled to a slider body of the slider, the endoscope insertion part is inserted to a position where a larger-diameter part provided in the endoscope insertion part abuts against a base end surface of an outer tube. Accordingly, the slider body can be coupled to a predetermined suitable position of the endoscope insertion part.
