A surgical system includes: an overtube including a channel into which an endoscope is inserted; and an expansion device configured to ensure a surgical space by expanding an interior of a body at a distal side relative to a tip of the overtube. The expansion device includes a sheath and a wire configured to be protrudable from the sheath. The wire is configured to be switchable between a first configuration in which the wire protrudes from the sheath and a second configuration in which the wire protrudes from the sheath in a state where the wire is tilted, around a longitudinal axis, at an angle different from the first configuration.