PURPOSE: To efficiently ozonize compressed air and to generate ozone of high concn. by coiling an insulated leading wire around a cylindrical inner discharger made of porous metallic plate and putting this discharger in a cylindrical outer discharger made of porous metallic plate.

CONSTITUTION: An insulation coated leading wire 5 is coiled around a cylindrical inner discharger 1 made of insulation coated porous metallic plate. The inside diameter of a cylindrical outer discharger 6 made of insulation coated porous metallic plate is made slightly larger than the outside diameter of the inner discharger 1 so as to easily put the discharger 1, and holes 4', 4 of the dischargers coincide with each other. The inner discharger 1 coiled with the wire 5 is unitedly put in the outer discharger 6 so that the holds 4', 4 are allowed to coincide with each other. An end of the wire 5 is connected to the positive pole of a high voltage transformer 7, and ends of the dischargers 1, 6 are connected to the negative pole through cords 8 to generate ozone.