A method for removing detrimental organic chlorine compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from a combustion waste gas, which comprises the steps of: bringing organic chlorine compounds contained in a combustion waste gas at a temperature within a range of from 150.degree. to 350.degree. C. into contact with a catalyst comprising at least one selected from the group consisting of platinum, palladium, ruthenium, manganese, copper, chromium and iron and oxides thereof, which catalyst is supported on the surface of a carrier containing at least titanium oxide, Aluminum oxide and silicon oxide, to cause a decomposition reaction of the organic chlorine compounds, thereby removing organic chlorine compounds from the combustion waste gas at a high efficiency.