PURPOSE: To supply ozone into a room successively and to make the ozone concentration in a room higher, by blowing outdoor atmospheric air by an air pump as an oxygen supplying source to an ozone generator, installing an air filter means on the suction side of the air pump and installing an oxygen supplying means via supplying quantity control means on the air pump suction side.

CONSTITUTION: Ozone generators 11-14 blow out generated ozone into a room 10 taking air in the room 10 in as the oxygen supplying source. An exhaust opening 15 to release air in the room is installed on the upper side of the room 10 and a plurality of ozone concentration sensor 16 is installed with different heights at the side wall of the room. Air pumps 20 and 21 forcibly blow air to the ozone generators 11-14 taking atmospheric air, i.e., natural air, as the oxygen supplying source. A filter means 30 is installed on the suction sides of the pumps 20 and 21. A central control means 50 is to control opening of an electromagnetic valve 41 responding to the concentration detection information from an ozone concentration sensor 16 and adjust the oxygen quantity supplied from an oxygen bomb 40 to the ozone generators 11-14.