An endoscope optical adapter attachment/detachment assisting tool includes: an assisting tool body configured to contain and hold an optical adapter attachable to and detachable from a distal end portion of an insertion portion of an endoscope an adapter seizing portion configured to come into contact with the optical adapter contained in the assisting tool body and press the optical adapter in a direction orthogonal to a direction of attaching and detaching the optical adapter to and from the distal end portion to seize the optical adapter and an urging member configured to urge an adapter holding portion.
