The endoscope 1 includes an insertion portion 2 that extends in the longitudinal direction, and a dual-purpose tube 16 that is inserted from the proximal side of the insertion portion 2 to the distal end portion 5. The distal end portion 5 of the insertion portion 2 is A first surface 31 orthogonal to the longitudinal axis 2 a, a second surface 32 that intersects adjacent to the first surface 31, and intersects adjacent to the first surface 31 and the second surface 32. And the opening 5m provided on the distal end 5 side of the dual-purpose tube 16 has three boundaries 35 on the first surface 31, the second surface 32, and the third surface 33. , 36 and 38 are arranged at a position including a point P where they intersect. 内視鏡１は、長手方向に延びる挿入部２と、この挿入部２の手元側から先端部５まで挿通される兼用チューブ１６と、を具備しており、挿入部２における先端部５は、長手方向軸２ａに直交する第１の面３１と、この第１の面３１に隣接して交差する第２の面３２と、第１の面３１及び第２の面３２に隣接して交差する第３の面３３と、を備え、兼用チューブ１６における先端部５側に設けられる開口５ｍは、投影面が第１の面３１、第２の面３２、第３の面３３における三つの境界３５、３６、３８が交わる点Ｐを含む位置に配置されている。
