PROBLEM TO BE SOLVED: To provide an insertion unit capable of easily locating a balloon ahead of bent parts since the unit can be made easily pass through the multiple bent parts.SOLUTION: The insertion unit comprises: an outside insertion body 10 an inside insertion body 20 movable in the outside insertion body 10 a balloon 22 which is provided at a tip side part of the inside insertion body 20, and which prevents gas A from approaching space P backward of a contact part W by expanding in a radial direction K and coming in contact with an inner wall 100n of a pipe conduit 100, in a state where the tip side of the inside insertion body 20 projects forward from a tip of the outside insertion body 10 and a fluid supply tube 23 inserted in the inside insertion body 20, for supplying fluid R to the balloon 22.
