PURPOSE: To make handling simple and to clean surely an optical system for observation even when the extent of curve of the inserting part of an endoscope is changed.

CONSTITUTION: A cleaning tube 13 being freely insertable and pullable out in a channel of an endoscope 1 is inserted from a channel opening part 12 and is perforated through the inserting part 2 and is projected from the apex to perform cleaning by ejecting a cleaning fluid to the apex including an optical system for observation. The cleaning tube 13 has a tube main body 14 and an apex chip 15 and ejecting holes ejecting the cleaning fluid are formed in two lines in the axial direction in a peripherally circulated shape on the apex chip 15. The distance between lines of this ejecting holes are set in such a way that it is in accordance with the width of changing of the amt. of projection of the apex chip 15 from the apex part 7 of the endoscope generated when the cirved part 8 of the inserting part 2 is curved and even when the extent of curve is changed, the cleaning fluid can be ejected to the optical system for observation.