Abstract: The present invention relates to a device for distributing liquid, especially washing liquid for washing paper pulp, in a diffuser having at least one screen plate (1), comprising an apparatus for supplying the washing liquid and at least one elongated nozzle (2, 5) which can be connected to the apparatus and which extends down in front of the screen plate and is arranged to supply the liquid. The nozzle is provided with openings (7 to 12) for washing liquid which open out at different predetermined levels, and whose location is designed to provide an even distribution of washing liquid along the height of the screen plate. A channel (13 to 18) for supplying washing liquid can be arranged to each opening (7 to 12) in the nozzle (2, 5).