PROBLEM TO BE SOLVED: To provide an overtube for an endoscope, in which a balloon can be prevented from damaging a tissue in the body when a distal end of the overtube is inserted into a narrow section of a digestive tract.SOLUTION: An overtube 1 for an endoscope includes: a tube body 2 into which the endoscope can be inserted a balloon 5 mounted on the distal end of the tube body 2 while the balloon 5 swells in an outer peripheral direction of the tube body 2 and an air supply/exhaust tube 4 for supplying a gas to the balloon 5. In the overtube 1 for the endoscope, the balloon 5 is formed by laminating two stretchable sheets 6 and 7 so as to expand by the supply of the gas to a gap of both sheets 6 and 7, and has an annular member 8 at the distal end, the gas supply/exhaust tube 4 is communicated with the gap of both sheets 6 and 7, and by pressurizing the annular member 8 to the distal end side, the balloon 5 can be expanded to the distal end side.
