PURPOSE: To make wavelength of generated ultraviolet rays variable and to enable generation of ultraviolet rays having plural ranges of wavelength in an ultraviolet rays generating device impressing high frequency electromagnetic field to a gas discharge chamber by constituting the gas discharge chamber to be operable using variable kinds of gas and variable pressure.

CONSTITUTION: In the process for washing glass provided with a transparent conductive film as a material for prepg. a liquid crystal display panel, an object to be treated 19 is set in a treating chamber 9 for the purpose of removing inorg. impurities, and the chamber 9 is evacuated by a second evacuating device 15. Then, a second high frequency coil 17 and a controlling power source 8 are operated while flowing gaseous N2 or Ar from a second gas feeding source 12; and high frequency electromagnetic wave is applied to the chamber 9. Then, the chamber 9 is evacuated leaving the object 19 to be treated as it is when org. impurities are removed, and O2 is introduced from the source 12. On the other hand, after evacuating the gas discharge chamber 1 with a first evacuating device 5, H2 is introduced from a first gas feeding source 3 to adjust the pressure in the chamber to a specified pressure and gas discharge is generated by operating a first high frequency coil 7 and a power source 8. Generated ultraviolet rays are irradiated on the object 19 to be treated through a window member 11.