An endoscope cleaning instrument detachably attachable to an insertion section of an endoscope from a distal end portion side of the insertion section includes a covering member having a tubular shape and being capable of covering, on an outer circumferential surface of a bending section connected consecutively to a proximal end of a distal end portion in the insertion section, a distal end side adhesive section disposed on a distal end side of the bending section and formed from an adhesive and a proximal end side adhesive section disposed on a proximal end side of the bending section and formed from the adhesive.