PURPOSE: To improve the inserting efficiency of an endoscope into a pipe by forming a bent part on an insertion part of the endoscope, fitting a pair of insertion guides with a fixed interval near the bent part and forming guide parts on the end parts of the opposed insertion guides with an interval.

CONSTITUTION: When the insertion part 14a of the endoscope 14 is inserted from the pipe 11 side, a part close to the bent part 14b of the endoscope 14 is inserted with a fixed distance from the wall face of the pipe 1 by sliding the guide parts 15c of the insertion guides 15 screwed on both the end parts of the bent part 14b, so that even if any foreign substance exists on the wall face, an objective lens and a light distributing lens mounted on the tip part of the insertion part 14b can be prevented from being damaged by the foreign substance and the frictional coefficient of the portion can be sharply reduced. Thus, the endoscope can be smoothly inserted.