Provided is a dilator capable of increasing the diameter of a hole formed on the wall of a digestive tract and the like while ensuring distal-end flexibility and maintaining pushability and torquability even when a shaft is longer and curved. A dilator includes a hollow shaft having an outer diameter that is smaller at a distal end than at a proximal end, and a grip portion connected to the proximal end of the shaft. A spirally-arranged protruding portion protruding outwardly is provided on an outer peripheral surface of the shaft. The spirally-arranged protruding portion has gaps between adjacent portions along a longitudinal axis of the shaft.
