PROBLEM TO BE SOLVED: To smoothly and easily guide the end of an insertion part of an endoscope outward from an opening in a sidewall of a tubular body without complicating operations and with a simple construction.SOLUTION: The opening 68 in the sidewall from which the end of the insertion part 12 of the endoscope 10 can be guided outward is arranged in the sidewall of a tube body 64 through which the insertion part 12 is inserted. A fixed guide member 70 which has a guide surface 70a for guiding the end of the insertion part 12 to the opening 68 in the sidewall is arranged near the end of an insertion passage 66 of the tube body 64. Also, an optically transparent window by which a field of vision in the direction of extension of the insertion part 12 can be ensured is arranged in the fixed guide member 70. In this manner, observation under direct vision can be made by an observation optical system 52 of the insertion part 12 through the window of the fixed guide member 70 without obstruction of the field of vision in the direction of extension of the insertion part 12. The end of the insertion part 12 can also be guided to the opening 68 in the sidewall along the guide surface 70a of the fixed guide member 70.
