PROBLEM TO BE SOLVED: To provide an introduction device which enhances maintainability.SOLUTION: An introduction device includes: an insertion part 21 which is provided with a gear part 34 a rotor 24 which is provided with a through-hole 25 for exposing a part of the gear part 34, which assumes a cylindrical shape surrounding the insertion part 21 in such a manner as to cover the gear part 34, and which can be rotated around the insertion part 21 by being engaged with the gear part 34 an elastic member 26 for closing the through-hole 25 and a holding unit 27 for holding the elastic member 26 with respect to the rotor 24.
