A treatment endoscope (10) includes that a body cavity insertion portion (12) which includes a main body distal hard portion (41), and a main body curving portion (42) provided to a proximal side of the main body distal hard portion (41), one or more treatment arm/arms (33, 34) projecting to a distal side from the main body distal hard portion (41), each of the treatment arm/arms (33, 34) including a curving mechanism (37, 38), an operation portion (19, 22) provided to the proximal side of the body cavity insertion portion (12), and an observation section (200) configured to image a field of view in a body cavity, the observation section (200) including an imaging section (202) provided within the main body distal hard portion (41) of the body cavity insertion portion (12). The treatment endoscope (10) includes that an operation portion attaching/detaching mechanism (A, B, C) configured to removably attach the operation portion (19, 22) to the body cavity insertion portion (12), and an observation section attaching/detaching mechanism (72, 205) configured to removably attach the observation section (200) to the body cavity insertion portion (12).
