An ultrasonic endoscope according to the present invention is an ultrasonic endoscope including an insertion portion that is inserted into a subject, and includes the longitudinal axis (N) of the insertion portion, and the longitudinal axis (N ) Having an ultrasonic transducer (71) that transmits and receives ultrasonic waves on a plane parallel to the ultrasonic wave function portion (214) provided at the distal end of the insertion portion, and a balloon having a groove shape capable of locking the balloon An endoscope function part (215) having at least a locking part (215e) and an imaging optical system and having an ultrasonic function part (214) detachable, the direction of the longitudinal axis (N) of the insertion part , The first plane (P1) that passes through the end portion (215) of the ultrasonic transducer (71) on the endoscope function portion side and is orthogonal to the longitudinal axis (N) of the insertion portion is an ultrasonic function. End function of the endoscope function section (215) that forms a boundary between the section (214) and the endoscope function section (215), the endoscope function section Situated in the ultrasonic function unit (214) side proximal to the second plane passing through the end portion (P2) of 215)本発明に係る超音波内視鏡は、被検体内に挿入される挿入部を備えた超音波内視鏡であって、該挿入部の長手軸（Ｎ）を含み、かつ該長手軸（Ｎ）に平行な面上で超音波を送受信する超音波振動子（７１）を有し、挿入部の先端に設けられる超音波機能部（２１４）と、バルーンを係止可能な溝形状をなすバルーン係止部（２１５ｅ）、および撮像光学系を少なくとも有し、超音波機能部（２１４）を着脱自在な内視鏡機能部（２１５）と、を備え、挿入部の長手軸（Ｎ）の方向において、超音波振動子（７１）の内視鏡機能部側（２１５）の端部を通過し、該挿入部の長手軸（Ｎ）と直交する第１の平面（Ｐ１）が、超音波機能部（２１４）と内視鏡機能部（２１５）との境界をなす内視鏡機能部（２１５）の端部であって、内視鏡機能部（２１５）の超音波機能部（２１４）側の端部を通過する第２の平面（Ｐ２）よりも基端側に位置する
