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 front-end flexibility and maintaining pushability and torquability even when a shaft is longer and curved. A dilator 80 includes a hollow shaft 81 having an outer diameter of a front end smaller than that of a base end, and a grip portion 9 connected to the base end of the shaft 81. A spirally-arranged protruding portion 82 protruding outwardly is provided on an outer peripheral surface 81B of the shaft 81. The spirally-arranged protruding portion 82 has gaps between adjacent portions along an axis A of the shaft 81.
