NOVELTY - The device (1) for producing hydrogen by electron cyclotron resonance, comprises a sealed vacuum chamber (2) to contain a plasma, a unit for injecting a high-frequency wave inside the chamber, a magnetic structure (3, 4, 5, 6, 7, 8, 9, 10) for generating a magnetic field in the chamber and generating a plasma according to the magnetic field lines, and a unit (14) for injecting steam in the chamber in the form of a supersonic jet. The module of the magnetic field has a magnetic mirror configuration with an electron cyclotron resonance area.    USE - The device is useful for producing hydrogen by electron cyclotron resonance, where the hydrogen is useful as energy carrier for producing petrol and other fossil fuels.    ADVANTAGE - The device is capable of efficiently, stably and continuously producing hydrogen by electron cyclotron resonance in an economical manner without producing greenhouse gas emissions and the use of carbon-carbon compounds or other chemical complexes.    DETAILED DESCRIPTION - The device (1) for producing hydrogen by electron cyclotron resonance, comprises a sealed vacuum chamber (2) to contain a plasma, a unit for injecting a high-frequency wave inside the chamber, a magnetic structure (3, 4, 5, 6, 7, 8, 9, 10) for generating a magnetic field in the chamber and generating a plasma according to the magnetic field lines, and a unit (14) for injecting steam in the chamber in the form of a supersonic jet. The module of the magnetic field has a magnetic mirror configuration with an electron cyclotron resonance area. The plasma electrons partially dissociate the water molecules introduced in the vapor phase and ionize the dissociation products. The magnetic mirror configuration is such that the module of the magnetic field has a minimum non-punctual constant and equals to the magnetic field corresponding to the electronic cyclotron resonance extended along the chamber. The plasma is present in the form of a sheet. The steam injecting unit comprises a flat nozzle, and a diverter. The diverter is intended to form the steam jet so that it is directed along an axis (AA') of the chamber. A selective cryogenic condenser (11) is present for freezing oxygen along the sheet of plasma generated in the chamber without freezing hydrogen obtained by the dissociation. A unit is arranged for recovering hydrogen obtained from the dissociation. The oxygen is trapped by the cryogenic condenser, which forms the internal wall of the chamber and is located at the minimum non-punctual magnetic field. The condenser is present in annular form surrounding the plasma present in the chamber, and has a temperature of 6-40 K for an average pressure of 10-3 mbar to 5x 10-3 mbar in the chamber. A second cryogenic condenser (12) is arranged at an end of the chamber between the magnetic mirror configuration and the hydrogen recovery unit for freezing the oxygen obtained from the dissociation. The magnetic structure comprises permanent magnets having same or different magnetization direction and different sizes, and coils at ambient temperature and/or superconducting coils having low or high critical temperature (Tc). Poles of the magnets are facing in the injection area of the steam or in the area of the hydrogen recovery. The permanent magnets located in the area for injecting water vapor have a different polarity of permanent magnets located in the hydrogen recovery area. A unit is arranged along the axis (AA') of steam injection for collecting non-dissociated water, and forms a diaphragm around the steam injection unit to define the steam jet. A system is arranged for reinjecting non-dissociated water in vapor phase. A grid having a mesh is arranged between the plasma of the chamber and the cryogenic condenser to control the propagation of high frequency waves. The grid is formed by a metal mobile cylinder comprising solid parts and pierced parts for the partial protection of the condenser from high frequency waves. The sealed vacuum chamber comprises a first chamber, and a second chamber. The first chamber is arranged to collect the oxygen, when the temperature of the condenser is high. The unit for collecting hydrogen is placed outside the magnetic mirror configuration, and comprises a unit for pumping hydrogen in the gas phase and another cryogenic condenser for freezing hydrogen. The second chamber is arranged for collecting hydrogen, when the temperature of another cryogenic condenser is high. The unit for injecting high frequency wave inside the chamber comprises an entrance window placed in a high magnetic field for the plasma diffusion towards the chamber thus avoiding plasma impact on the window. The module of the minimum magnetic field is 90% of the electronic cyclotron resonance value. A unit is arranged for injecting multifrequencies of high-frequency waves.    DESCRIPTION OF DRAWING(S) - The figure shows a top view of a device for producing hydrogen.    Hydrogen production device (1)    Chamber (2)    Magnetic structure (3, 4, 5, 6, 7, 8, 9, 10)    Selective cryogenic condenser (11)    Second cryogenic condenser (12)    Steam injecting unit. (14)