Provided are a surgical apparatus for an endoscope and an exterior tube that can supply a pneumoperitoneum gas into a body cavity without causing degradation of operability. An exterior tube 500 is sheathed to an outer tube insertion part 321 of an outer tube that is inserted into a body cavity through a body wall and guides an endoscope and a treatment tool into the body cavity, and an outer peripheral surface of the exterior tube 500 is provided with a locking part that restricts the forward and backward movement of the exterior tube 500 with respect to the body wall and the rotation of the exterior tube around an axis. A gap between an inner peripheral surface 500b of the exterior tube 500 and an outer peripheral surface 320a of the outer tube insertion part 321 is used as an air supply passage 574 for supplying the pneumoperitoneum gas within the body cavity.
