To provide a dilator for an ultrasonic endoscope that has improved ultrasonic visibility.SOLUTION: A dilator 3 for an ultrasonic endoscope is constituted of a flexible tube that includes: an expansion part having a tapered part 31b having a tapered shape in the tip part thereof and a straight trunk part 31d positioned in the vicinity of a base end part side of the tapered part； and a lumen through which a guide wire is slidably inserted. A rough surface 33a is provided partially or wholly in the expansion part.SELECTED DRAWING: Figure 13【課題】超音波視認性を向上した超音波内視鏡用ダイレータを提供する。【解決手段】先端部に先細のテーパ部３１ｂおよび該テーパ部の基端部側近傍に直胴部３１ｄを有する拡張部と、ガイドワイヤが摺動可能に挿通される内腔とを有する可撓性チューブからなる超音波内視鏡用ダイレータ３であって、前記拡張部の全部または一部に粗面３３ａを設けた。【選択図】 図１３
