PURPOSE: To obtain activated oxygen with a good productive efficiency by the miniaturized device which eliminates the need of dehumidification and is free from the generation of NOx, by exciting and radiating an ultraviolet ray lamp enclosing Xe and halogen gas in a specified polycrystal ceramic tube in O2-gas or O2-containing gas.

CONSTITUTION: Caps 12 made of Nb, etc., are hermetically fitted to both ends of the tube 11 made of polycrystal ceramics having the light transmitting range of at least 150W180nm and 200W300nm wave length ranges, and the ultraviolet ray lamp 1 is constituted in such a way that electrodes 13 consisting of stainless tubes 14 and double coils 15 applied with emitter are fixed to the caps and halogen gas and the rare gas the main component of which is Xe is enclosed in the inner part of tube so as to be the pressure of 50W500Torr. The above- mentioned ultraviolet ray lamp 1 is installed in the rectangular casing 3 of an activated oxygen producing device to be excited and radiated by an electric power source 2 provided in the casing 3, and O2-containing gas, such as air, is introduced by a blower 5 through a filter 5 provided on one end opening of the casing 3 to ozonize and decompose it to produce activated oxygen.