To provide a dilator capable of easily expanding the diameter of a hole formed in a wall of a digestive tract or the like.SOLUTION: A shaft 21 of a dilator 20 includes a tapered portion 24 having the outer diameter of the tip smaller than the outer diameter of the base end, a tip portion 25 provided on the tip side of the tapered portion 24 and a base end portion 23 provided on the base end side of the tapered portion 24 or a base end portion 23 provided on the base end side of the tapered portion 24 without having the tip portion. When the shaft 21 does not have a tip portion but has the base end portion 23, the pitch of the adjacent portion along an axis A of a spiral convex portion 22 provided in the tapered portion 24 is smaller than the pitch of adjacent portion along the axis A of the spiral convex portion 22 provided in the base end portion 23. When the shaft 21 has the base end portion 23 and the tip portion 25, the pitch of the adjacent portion along the axis A of the spiral convex portion 22 provided in the tapered portion 24 is smaller than the pitch of adjacent portion along the axis A of the spiral convex portion 22 provided in the tip portion 25 or the base end portion 23.SELECTED DRAWING: Figure 3【課題】消化管等の壁に形成された孔を容易に拡径することができるダイレータを提供する。【解決手段】ダイレータ２０のシャフト２１は、先端の外径が基端の外径よりも小さいテーパ部２４と、テーパ部２４の先端側に設けられた先端部２５およびテーパ部２４の基端側に設けられた基端部２３と、または、前記先端部を有さずに、テーパ部２４の基端側に設けられた基端部２３とを有する。シャフト２１が先端部を有さず基端部２３を有する場合、テーパ部２４に設けられた螺旋状の凸部２２の軸Ａに沿って隣り合う部分のピッチは、基端部２３に設けられた螺旋状の凸部２２の軸Ａに沿って隣り合う部分のピッチよりも小さく、シャフト２１が基端部２３および先端部２５を有する場合、テーパ部２４に設けられた螺旋状の凸部２２の軸に沿って隣り合う部分のピッチは、先端部２５または基端部２３に設けられた螺旋状の凸部２２の軸Ａに沿って隣り合う部分のピッチよりも小さい。【選択図】図３
