A fastening device (1) in plastic material has a sleeve (9), which can be fastened to a disposable hose (4) and defines an axial seat (10), which is a through one and is engaged, in use, by the end (2) of an endoscope (3) with an interference coupling the sleeve (9) has at least one weakening (37) which makes the inside of the sleeve (9) elastically yielding in a circumferential direction, so as to adapt the perimeter of the seat (10) to the dimensional tolerances of the end (2) of the endoscope (3).
