Disinfector / sterilizer (1) for disinfecting / sterilizing endoscopes comprising: a frame (2)； a cover (3) covering the frame (2)； the frame (2) and the cover (3) formed relative to one another to define at least one tunnel (4) having a first opening (5) and a second opening (6) which is opposite the first opening being (5 )； a top wall (7) which at least partially delimits the tunnel at the top (4)； a first side wall (11) which can be placed in the first opening (5) to obstruct the tunnel (4)； a second side wall (12) which can be placed in the second opening (6) to block the tunnel (4)； disinfector / sterilizer (1) being characterized in that: it comprises a trough (9) sized to receive at least an endoscope to be disinfected / sterilized and is sized to move along the tunnel (4)； comprises a cup support (10) fixed to the tray (9), forming the cuvette holder (10) and the cuvette cuvette group (9, 10)； comprises guide means (8) to guide the group bowl (9, 10) along the tunnel (4) between: a first end area (A1) in which the tray (9) projects outwardly from the first opening (5) of the tunnel (4) to be accessible for inserting or removing the at least one endoscope； and a second end area (A2) in which the tray (9) projects outwardly from the second opening (6) of the tunnel (4) to be accessible for inserting or removing the at least one endoscope； forms the top wall (7), with the bowl (9), a closed chamber (13) to disinfect / sterilize the at least one endoscope when the bucket (9) is inside the tunnel (4)； the first side wall (11), when in the first opening (5) can be coupled alternately and removably: the frame (2) to be solidly constrained to the frame (2) and obstructing the tunnel (4)； or with the cuvette holder (10) to be solidly constrained to, and be extracted by the group bowl (9, 10) and allow the group cuvette (9, 10) reaches the first end area (A1)； the second side wall (12), when in the second opening (6), can engage alternatively and removably: the frame
