The invention relates to a powder diffuser nozzle (2) for an electrostatic dusting device, which is designed to be positioned at the end of an applicator gun. The inventive nozzle (2) comprises: a lateral wall (49) which defines a passage that extends from the powder conduit (8) of the gun (3), and a base (56) which seals said conduit (8) at the end thereof. In addition, a port (57) is provided in the lateral wall (49) close to the base (56) in order to connect the powder conduit (8) with the exterior of the nozzle (2). The axis (A1) of the port (57) forms a determined angle (A) with the axis (A2) of the powder conduit (8). Moreover, at least one deflector (58) is provided on the base of the nozzle (56) or on the lateral wall (49) close to said base in order to divert the jet of powder from the conduit (8) along the axis (A1) of the port (57).