To provide an endoscope assisting device capable of changing an inner diameter of a treatment instrument insertion channel of an endoscope according to situations, stabilizing arrangement of a treatment instrument insertion channel at an exit part and performing suction, and an endoscope capable of fitting the endoscope assisting device.SOLUTION: An endoscope assisting device 100 removably fitted to a treatment instrument insertion channel 23 of an endoscope 2 comprises a flexible tubular member 101 longer than a full length of the treatment instrument insertion channel 23l. The tubular member has a treatment instrument insertion duct 107 and a suction duct 108. An end part 103 of the tubular member has: a slide contact part 105 which has an outer periphery in slide contact with an inner peripheral surface of an exit part 25 of the treatment instrument insertion channel held straight regardless of curve of a curved part 15 of the endoscope and is arranged at the exit part； and an extension part 106 which extends from the slide contact part to a distal end side, and arranged protruding from the exit of the treatment instrument insertion channel. A distal end side opening of the suction duct is provided at the extension part.SELECTED DRAWING: Figure 9【課題】状況に応じて内視鏡の処置具挿通チャンネルの内径を変更可能であり、且つ処置具挿通チャンネルの出口部分における処置具の配置を安定させることができ、且つ吸引も行うことができる内視鏡補助具を提供し、この内視鏡補助具を取り付け可能な内視鏡を提供する。【解決手段】内視鏡２の処置具挿通チャンネル２３に着脱可能に取り付けられる内視鏡補助具１００は、処置具挿通チャンネル２３の全長より長い可撓な管状部材１０１を備え、管状部材は、処置具挿通管路１０７と、吸引管路１０８と、を有し、管状部材の先端部１０３は、内視鏡の湾曲部１５の湾曲にかかわらず直管状に保たれる処置具挿通チャンネルの出口部分２５の内周面に摺接する外周を有し、出口部分に配置される摺接部１０５と、摺接部から先端側に延びており、処置具挿通チャンネルの出口から突出して配置される延設部１０６と、を有し、吸引管路の先端側開口は、延設部に設けられている。【選択図】図９
