Provided are a surgical apparatus for an endoscope and an outer tube that ease limitation of the types of available medical instruments to improve convenience and improve operability. 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 therein a slider 400 that is an interlocking member that moves the endoscope and the treatment tool forward and backward in an interlocking manner. The slider 400 is provided with a cylindrical pressure-contact member 446 that is brought into pressure-contact with and coupled to an outer peripheral surface of the treatment tool. The pressure-contact member 446 is formed of compressible foamed rubber having pores, and an oil component is held in the pores of the foamed rubber.
