A method of recovering carbon dioxide, includes bringing gas to be processed containing carbon dioxide (CO2) and oxygen into contact with the CO2-absorbing solution in an absorption column to form a CO2-rich solution; circulating the solution in a regeneration column to thermally release and recover CO2 and recirculating the absorbing solution as a CO2-poor solution inside the absorption column; and performing heat exchange between the solution being delivered from the absorption column to the regeneration column and the solution recirculated from the regeneration column to the absorption column, wherein an alkanolamine aqueous solution containing a silicone oil and/or an organosulfur compound is added to the solution inside the absorption column and/or the solution recirculated from the regeneration column to the absorption column to adjust the composition of the absorbing solution inside the absorption column.