Abstract: The present invention provides a low-cost carbon dioxide fixation method that allows effective usage of a large amount of generated coal ashes, and effective fixation of carbon dioxide included in flue gas generated from coal, refuse, or waste product, as well as improvement in the applicability of coal ashes to various applications and effective usage of by-product carbonate. Carbon dioxide is absorbed and fixated by subjecting the flue gas to gas-liquid contact with coal ash water slurry or coal ash eluate so as to make the carbon dioxide in the flue gas react and be absorbed thereinto, thereby fixating the carbon dioxide as carbonate. This method can be favorably used for disposal of flue gas from a boiler at a coal thermal power plant.