PURPOSE: To provide the titled apparatus constituted so as to enlarge a contact area with an earth electrode and the malodorous gas as well as to agitate the stream of the malodorous gas to cool an O3-generator with the low flow rate malodorous gas in good efficiency, by charging a packing material in the space between the earth electrode and a malodorous gas duct of the O3-generator.

CONSTITUTION: A malodorous gas is flowed through the filler material 8 in the outside of the earth electrode tube 4b of an O3-generator 4 mounted in a malodorous gas duct 3 through a malodorous gas duct 2 by a blower 1. A contact area of the O3-generator is enlarged by charging a packing material 8 and a turbulent stream is generated in the malodorous gas, and heat transmission ratio to the electrode tube 4b is made large by the low flow rate malodorous gas to cool the electrode tube 4b in good efficiency. On the other hand, air is supplied into the malodorous gas passing through the duct 3 from a stock air inlet 4f to be mixed with ozonized air generated in a discharge space 4c and supplied into the duct 3. The resulting mixed gas is sent into a reaction tower 7 and contacted with filled catalyst in the tower 7 to be deodorized by the action of O3 to be discharged into the atmosphere.