A method for removing an acidic gas from a raw gas containing the acid gas by contacting the raw gas with an aqueous alkanol amine solution, characterized in that a composition comprising an organopolysiloxane containing a polyoxyalkylene group and a fine silica powder is caused to be present. In some embodiments, a composition comprising the above-mentioned organopolysiloxane and a fine silica powder is added appropriately according to the state of foaming in an acidic gas removing reaction system from the outside of the system, or use is made of an alkanol amine containing in advance a composition comprising the above-mentioned organopolysiloxane and a fine silica powder. In preferred embodiments, the fine silica powder has a specific surface area of 50 m2/g or more, and/or the composition comprising the above-mentioned organopolysiloxane and a fine silica powder is used in an amount of 0.1 to 5000 ppm relative to the alkanol amine. As a further embodiment, a method for removing an acidic gas from a raw gas by contacting the raw gas with an aqueous alkanol amine solution containing 40 mass % or more of an alkanol amine, characterized in that a composition comprising the above-mentioned organopolysiloxane and a fine silica powder is caused to be present in an amount of 0.1 to 5000 ppm relative to the alkanol amine.