PROBLEM TO BE SOLVED: To provide an advance/retreat assisting tool of an endoscope processing device capable of advancing/retreating the processing device, with a grip part of an endoscope to be held with one hand and an insertion part of the endoscope to be held with the other hand, without imposing a burden on one hand or obstructing an operation of one hand.SOLUTION: An advance/retreat assisting tool 100 includes: a base unit 110 a fixing unit 130 for fixing the base unit 110 to an endoscope 10 an advance/retreat unit 150 that advances/retreats along a direction of a central axis 111d of an insertion hole with respect to the base unit 110 to advance/retreat a processing device 51 in the longitudinal axis direction of the processing device 51 and an extension part coupled with the advance/retreat unit 150. The advance/retreat assisting tool 100 further includes a long part 180 that is coupled with the extension part and advances/retreats along the longitudinal axis direction to advance/retreat the advance/retreat unit 150 via the extension part.
