To take out ozone at a specified concentration from a container filled with silica gel on which ozone is saturatedly adsorbed by adjusting a temperature increasing speed for changing the cooling temperature of an ozone storage container to take out zone adsorbed on the silica gel.

In a storage container 1 cooled by ethanol in an outer box 3 composed of a heat insulating box, oxygen gas led out from a raw oxygen supply source 11 is converted into ozone by an ozone generator 9 to make mixed gas of ozone-oxygen and this is controlled to have a constant flow rate by a flow rate controller 10 and then supplied. The mixed gas of ozone-oxygen supplied to the storage container 1 is caused to act on a silica gel 2 filling the storage container 1 and selectively adsorbed, and remaining oxygen gas is discharged from an ozone discharge route 17. Taking-out of ozone gas adsorbed on the silica gel 2 is carried out by changing the cooling state of the storage container 1, and the taken-out gas is supplied via an ozone leasing- out route 6 and a flow passage opening/closing valve 12 to fill a container 13.