PROBLEM TO BE SOLVED: To provide an ultrasound endoscope which has the tip rigid portion of the insertion section distal end reduced in size in a longitudinal direction, with excellent operability.SOLUTION: In the tip rigid portion are arranged a side view-type optical observation portion and an ultrasound send/receive surface of an ultrasound probe on a side opposite a crosswise one side across a boundary side wall, which is one of a pair of side walls constituting a lateral opening recess that opens laterally. The ultrasound send/receive surface is arranged in a range at least a portion of which overlaps the boundary side wall, while being positioned differently from a raising base in a longitudinal direction of the insertion section. In addition, the apex of the raising base is positioned on a virtual line connecting the outer shape center of the ultrasound send/receive surface of the ultrasound probe and the crosswise center of a tip connection portion of a treatment instrument conduit line as viewed from a side in an observation direction of the optical observation portion toward the tip rigid portion.SELECTED DRAWING: Figure 3【課題】挿入部先端の先端硬性部の長手方向の小型化と優れた操作性を両立した超音波内視鏡を得る。【解決手段】先端硬性部に、側方に向けて開口する側方開口凹部を構成する一対の側壁の一方である境界側壁を挟んで幅方向の片側と反対側に側視型の光学観察部と超音波プローブの送受波面を配する。送受波面は、挿入部の長手方向において、起上台とは位置を異ならせつつ、少なくとも一部が境界側壁と重なる範囲に配置される。さらに、光学観察部の観察方向である側方から先端硬性部を見て、超音波プローブの送受波面の外形中心と処置具管路の先端接続部の幅方向の中心とを結ぶ仮想線上に起上台の頂部を位置させる。【選択図】図３
