A cover-adapted treatment endoscope (10) includes an endoscope cover (13) which covers an endoscope main body (21). The endoscope cover (13) includes a cover insertion portion main body (25), the cover insertion portion main body (25) including an insertion passage (20) into which the endoscope main body (21) is inserted, a cover distal end portion (91) provided at a most distal side portion, and a cover bending portion (92) which is provided to the proximal side of the cover distal end portion (91) and which is configured to be bent in response to the bending of a main body bending portion (33) of the endoscope main body (21) in an attached condition where the endoscope main body (21) is inserted in the insertion passage (20), a positioning mechanism (139) configured to determine an insertion position of the endoscope main body (21) where the main body distal portion (32) does not project from a distal end of the cover insertion portion main body (25) in the attached condition, a coupling portion (27) which couples the endoscope main body (21) to the cover insertion portion main body (25) in the attached condition, and one or more treatment arm/arms (45, 46) which projects/project from the distal end of the cover insertion portion main body (25) toward a distal side and each of which includes a bending mechanism (101, 102).
