A liquid diffusing device with interchangeable nozzles, comprising a support frame (2) having a passageway (3) for the liquid to be diffused, with an inlet (4) and an outlet (5), at least one nozzle (6), having a liquid outlet section (7) with a predetermined diameter and a corresponding outflow rate, which is removably and selectively attachable to the outlet (5) in a predetermined operating position, means for supporting at least one additional nozzle (6′, 6″, . . . ) having an outlet section (7′, 7″, . . . ) of a diameter other than that of the first nozzle (6), in the non-operating position. The support means comprise a nozzle-holding plate (8) formed of one piece with the frame (2) and having quick connect/disconnect means (9) for the additional nozzle (6′, 6″, . . . ) in the non-operating position.