Sterilization method using plasma for sterilizing objects, comprising the steps of: - introducing the objects to be sterilized into a sterilization chamber defined by an environment hermetically separated from the outside, - bringing said sterilization chamber to pressures lower than atmospheric pressure by means of a vacuum pump, - activating a plasma generator device disposed on at least one feed pipe leading to said sterilization chamber so that one or more gaseous compounds comprising a mixture of reactive oxygen species and of reactive nitrogen species, and optionally free ions with positive charge, are generated by the plasma generator device and conveyed to said sterilization chamber, - feeding air along said at least one feed pipe and putting the latter in communication with said sterilization chamber for a determinate period of time to allow said gaseous compounds to enter said sterilization chamber and spread in a substantially homogeneous way therein, said period of time being, for example, equal to or more than the activation time of said plasma generator device, said air being the carrier fluid which conveys the gaseous compounds into said sterilization chamber, - controlling, by means of a control unit, the electric power used to produce the plasma during said activation step of the plasma generator device as a function of the composition and/or the quantity of reactive species present in said sterilization chamber, detected by suitable sensor means; characterized in that said feed pipe has a square section, in that said plasma generator device comprises four electrodes on the walls (17A, 17B, 17C, 17D) of said feed pipe, according to a configuration able to optimize the electro-hydrodynamic effect so as to increase the quantity of reactive species produced in the unit of time, wherein each electrode is disposed on a respective wall (17A, 17B, 17C, 17D) of said feed pipe; and in that each of said electrodes has a circular or polygonal shape defining a configuration of symmetry with respect to a central axis of symmetry. - introducing the objects to be sterilized into a sterilization chamber defined by an environment hermetically separated from the outside, - bringing said sterilization chamber to pressures lower than atmospheric pressure by means of a vacuum pump, - activating a plasma generator device disposed on at least one feed pipe leading to said sterilization chamber so that one or more gaseous compounds comprising a mixture of reactive oxygen species and of reactive nitrogen species, and optionally free ions with positive charge, are generated by the plasma generator device and conveyed to said sterilization chamber, - feeding air along said at least one feed pipe and putting the latter in communication with said sterilization chamber for a determinate period of time to allow said gaseous compounds to enter said sterilization chamber and spread in a substantially homogeneous way therein, said period of time being, for example, equal to or more than the activation time of said plasma generator device, said air being the carrier fluid which conveys the gaseous compounds into said sterilization chamber, - controlling, by means of a control unit, the electric power used to produce the plasma during said activation step of the plasma generator device as a function of the composition and/or the quantity of reactive species present in said sterilization chamber, detected by suitable sensor means; characterized in that said feed pipe has a square section, in that said plasma generator device comprises four electrodes on the walls (17A, 17B, 17C, 17D) of said feed pipe, according to a configuration able to optimize the electro-hydrodynamic effect so as to increase the quantity of reactive species produced in the unit of time, wherein each electrode is disposed on a respective wall (17A, 17B, 17C, 17D) of said feed pipe; and in that each of said electrodes has a circular or polygonal shape defining a configuration of symmetry with respect to a central axis of symmetry.