PURPOSE: To carry out the removal of a S-compound by oxidation in good efficiency, by contacting a mixed gas wherein O3 is added and mixed with a maolodorous gas containing the S-compound with an activated carbon catalyst added and deposited with I2.

CONSTITUTION: A malodorous gas containing an S-compound such as H2S, lower alkylmercaptan or methyl sulfide is subjected to oxidation treatment as described hereinafter. That is, O3 is added to the malodorous gas in concn. of 0.5W 10 times, especially 2W5 times with regard to that of the S-compound contained in said malodorous gas and the resulting mixed gas is subsequently contacted with activated carbon having I2 supported therewith to remove the S-compound by oxidation. The aforesaid activated carbon is usual activated carbon obtained from coconut husk or charcoal and one in which fine pores with pore sizes of 100 or less are developed is preferred. In addition, the support amount of I2 is 0.1W10g, especially, 1W5g basing on 100g usual activated carbon.