To provide a dilator which can easily enlarge a diameter of a hole formed on a wall of digestive tract or the like.SOLUTION: A shaft 21 of a dilator 20 includes a tapered part 24 in which an outer diameter of a distal end is smaller than an outer diameter of a proximal end, a distal end part 25 provided on a distal end side of the tapered part 24, and a proximal end part 23 provided on a proximal end side of the tapered part 24, or includes the tapered part and the proximal end part 23 provided on the proximal end side of the tapered part 24 without having the distal end part. When the shaft 21 has the proximal end part 23 without having the distal end part, a pitch in an adjacent part of spiral protruding parts 22 provided on the tapered part 24 along an axis A is smaller than a pitch in an adjacent part of the spiral protruding parts 22 provided on the proximal end part 23 along the axis A. When the shaft 21 has the proximal end part 23 and the distal end part 25, a pitch in adjacent parts of the spiral protruding parts 22 provided on the tapered part 24 along the axis is larger than a pitch in adjacent parts of the spiral protruding parts 22 provided on the distal end part 25 or the proximal end part 23 along the axis A.SELECTED DRAWING: Figure 1【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大きい。【選択図】図１
