One ozone concentrating chamber is provided therein with a part of a cooling temperature range where ozone can be selectively condensed or an oxygen gas can be selectively removed by transmission from an ozonized oxygen gas, and a part of a temperature range where condensed ozone can be vaporized, and condensed ozone is vaporized by moving condensed ozone with flow of a fluid or by gravitation to the part where condensed ozone can be vaporized, whereby the ozonized oxygen gas can be increased in concentration. Such a constitution is provided that a particle material 13 for condensation and vaporization filled in the ozone concentrating chambers 11 and 12 has a spherical shape of a special shape with multifaceted planes on side surfaces, or an oxygen transmission membrane 130 capable of selectively transmitting an oxygen gas in an ozone gas is provided.