A nozzle for distributor devices of granule's growth liquid substance in fluid bed granulators, is distinguished by the fact that it comprises a first duct (2), with substantially rectilinear axis (A) and with a predetermined diameter, which duct has an end portion (3) including a supply opening (4) and made of at least twosubsequent segments, a first cone-shaped segment (5) converging on the axis (A) and a further cone-shaped segment (7) diverging from the axis (A) and ending in the supply opening (4), a second duct (8) extending co-axially inside the first duct (2), with which it forms an annular space (9), the second duct (8) having a supply end (10) extended inside the first cone-shaped segment (5) of the first duct (2).