An insertion device assembly for nasal sinuses includes: a guide pipe bent portion on the distal side of the guide pipe main body a guide pipe distal opening on the distal side of the bent portion a sheath inserted into the bent portion and the guide pipe distal opening from a proximal side opening of the main body through the main body to be movable back and forth a sheath distal opening at the distal side of the sheath an insertion portion of an endoscope inserted through the sheath to be movable back and forth and an endoscope operation portion passing the sheath distal opening and the distal end of the insertion portion of the endoscope through the bent portion and protruding the distal end of the insertion portion of the endoscope from the guide pipe distal opening.
