An absorption column is equipped with: a CO2 absorption section absorbing CO2 from CO2-containing exhaust gas using a lean solution; a main rinse section recovering an entrained CO2 absorbent using rinse water; a rinse water circulation line circulating a rinse water containing the CO2 absorbent recovered in a liquid storage section of the main rinse section; a pre-rinse section provided between the CO2 absorption section and the main rinse section; a rinse section extraction liquid supply line extracting a portion of the rinse water containing the CO2 absorbent from the rinse water circulation line, and introducing the same into a reflux section of an absorption liquid regeneration tower; and a refluxed water supply line extracting a portion of refluxed water, introducing the same as pre-rinse water for the pre-rinse section, and connected on the pre-rinse section side.