An endoscope optical adapter attachment/detachment assisting tool 30 includes: an assisting tool body 31 configured to contain and hold an optical adapter 20 attachable to and detachable from a distal end portion 11 of an insertion portion 2 of an endoscope 10 an adapter seizing portion 33a, 36, 43 configured to come into contact with the optical adapter 20 contained in the assisting tool body 31 and press the optical adapter 20 in a direction orthogonal to a direction of attaching and detaching the optical adapter 20 to and from the distal end portion 11 to seize the optical adapter 20 and an urging member 33, 39, 46 configured to urge an adapter holding portion.
