NOVELTY - Pressure-risen sewage gas and water are contacted, carbon dioxide and sulfur-type impurities contained in sewage gas are dissolved in high-pressure water, carbon dioxide and sulfur-type impurities are separated from sewage gas, resultant methane gas are purified, hydrogen is added to purified gas, and supplied to catalyst tower (8) where catalyst (7) is filled with purified gas to which hydrogen is added. The catalyst converts oxygen remained in the purified gas to which hydrogen is added, into water by catalytic reaction. Thus, deoxidization of sewage gas is carried out.    USE - Deoxidization of sewage gas.    ADVANTAGE - The sewage gas is efficiently deoxidized and purified.    DETAILED DESCRIPTION - Sewage gas emitted by methane-fermenting organic waste is compressed and pressure-risen using a compressor (2a,2b), pressure-risen sewage gas is supplied to an absorption tower (3), pressure-risen sewage gas and water are contacted at high-pressure state in the absorption tower, carbon dioxide and sulfur-type impurities which are contained in the pressure-risen sewage gas are dissolved in high-pressure water, and the carbon dioxide and sulfur-type impurities are separated from the pressure-risen sewage gas, resultant methane gas are purified, hydrogen is added to purified gas, and purified gas to which the hydrogen is added is supplied to catalyst tower where catalyst is filled with purified gas to which the hydrogen is added. The catalyst converts oxygen remained in the purified gas to which the hydrogen is added, into water by catalytic reaction. Obtained water is removed, and electrolyzed to obtain the hydrogen. Thus, deoxidization of sewage gas is carried out. An INDEPENDENT CLAIM is included for deactivator.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the deactivator used during deoxidization of sewage gas. (Drawing includes non-English language text)    Gas compressors (2a,2b)    Absorption tower (3)    Water supply tank (4)    Palladium catalyst (7)    Catalyst tower (8)