PURPOSE: To prevent infeasibility of ion irradiation by providing cups made of ceramics to the negative potential electrode of ion lead-out electrodes in an ionizing chamber of an ion treating device, and irradiating the electron showers by the plasma produced in the cups to a substrate.

CONSTITUTION: A magnetic field is formed in an ionizing chamber 1 by an exciting solenoid 2, and microwaves are introduced therein through a waveguide 3 to generate cyclotron resonance in the chamber 1, thereby generating plasma. The ions thereof are led out by lead-out electrodes 4 and are irradiated to a substrate 7 in a reaction chamber 5, whereby the substrate is ion-treated. Cups 10 made of insulators such as ceramics are installed to the negative potential electrode 4b out of the electrodes 4, and plasma of negative potential is generated in the cups. The electrons showers leading out the electrons thereof by the ground potential electorde 4c out of the electrodes 4 are irradiated together with the ion showers to the substrate 7. The infeasibility of ion irradiation owing to electrostatic charging does not occur even if the substrate is an insulator.