Apparatus (10; 110) for the micronization of a powdered material or product (P) comprising a micronizer mill (20), of the type with high-energy jets of a gaseous fluid, in turn comprising a micronization chamber (20a), in which micronization chamber the powdered material (P) is micronized as a result of the collisions between its particles caused by the high-energy jets (G) of a first gaseous fluid (A), such as nitrogen or air, wherein the micronization chamber (20a) of the micronizer mill (20) is delimited by walls (20f) which have at least one porous portion which is traversed by a regular flow (f1), of a second gaseous fluid (F), aimed towards the interior of the micronization chamber, so as to avoid the formation of incrustations and/or accumulations of powdered material in the same micronization chamber (20a). More particularly the micronization apparatus (10) comprises a first outer annular chamber (20b) which extends around the micronization chamber (20a) and is fed by the first gaseous fluid (A) which generates the high-energy jets in the micronization chamber, and a second intermediate annular chamber (20d) which is associated with the porous wall (20f) which delimits the micronization chamber (20a) and is fed by the second gaseous fluid (F) aimed to flow through this porous wall, or, in a variant (110) of the micronization apparatus, comprises instead of the first annular chamber a system of channels (120b) which convey the first gaseous fluid which generates the high-pressure jets and extend through the annular chamber (120d) fed by the second gaseous fluid (F) which traverses the porous wall. Advantageously the apparatus of the invention (10; 110), avoiding the formation of incrustations and similar accumulations inside the micronization chamber (20a) of the micronization mill (20) and in the adjacent areas, improves the efficiency of the micronization process and the quality of the micronized end product and moreover considerably reduces the costs of maintenance with respect to conventional micronization mills and apparatuses, with high-energy jets of a gaseous fluid.