An apparatus for treating used absorbent sanitary products includes a rotary cylindrical autoclave having a side wall and two ends, at least one of which terminates in a hatch that can be opened to enable access to the autoclave and sealably closed to enable pressurization of the autoclave; a circuit for heating and pressurizing the autoclave for heating the absorbent sanitary products to a sterilization temperature; and a plurality of cutting nozzles supplied by pressurized fluid, which are arranged for directing respective jets of pressurized fluid inside the autoclave.