A CO 2 recovery unit comprising: an absorbing tower that allows absorbing liquid to absorb CO 2 in exhaust gas; and a regeneration tower that allows the absorbing liquid that absorbed CO 2 in the absorbing tower to discharge CO 2, wherein the absorbing liquid that discharged CO 2 in the regeneration tower is reused in the absorbing tower, wherein the regeneration tower includes: a first regeneration portion having a first tray portion that stores the absorbing liquid; a second regeneration portion provided below the first regeneration portion and having a liquid dispersion portion that supplies the absorbing liquid and a second tray portion that stores the absorbing liquid; and a first supply pipe (L 5) that connects the first tray portion and the liquid dispersion portion to supply the absorbing liquid stored in the first tray portion to the liquid dispersion portion, characterized in that the first supply pipe (L 5) includes a heating portion that is configured to obtain a thermosiphon effect by heating the absorbing liquid and by partially vaporizing the absorbing liquid such that the first supply pipe (L 5) is configured to circulate the absorbing liquid using a density difference between the absorbing liquid flowing before the heating portion and the absorbing liquid flowing after the heating portion as a driving force, wherein the first supply pipe (L 5) does not have a pumping device that pumps the absorbing liquid or a control portion that controls a flow rate of the absorbing liquid, the liquid dispersion portion is positioned lower than a connecting portion with which the first supply pipe (L 5) and the first tray portion are connected, and the first supply pipe (L 5) or the heating portion partially includes a portion disposed higher than an extraction position of the absorbing liquid from the first regeneration portion, and the first supply pipe has a further portion in which the absorbing liquid flows after exiting the heating portion; said further portion being disposed higher than the heating portion. an absorbing tower that allows absorbing liquid to absorb CO 2 in exhaust gas; and a regeneration tower that allows the absorbing liquid that absorbed CO 2 in the absorbing tower to discharge CO 2, wherein the absorbing liquid that discharged CO 2 in the regeneration tower is reused in the absorbing tower, wherein the regeneration tower includes: a first regeneration portion having a first tray portion that stores the absorbing liquid; a second regeneration portion provided below the first regeneration portion and having a liquid dispersion portion that supplies the absorbing liquid and a second tray portion that stores the absorbing liquid; and a first supply pipe (L 5) that connects the first tray portion and the liquid dispersion portion to supply the absorbing liquid stored in the first tray portion to the liquid dispersion portion, a first regeneration portion having a first tray portion that stores the absorbing liquid; a second regeneration portion provided below the first regeneration portion and having a liquid dispersion portion that supplies the absorbing liquid and a second tray portion that stores the absorbing liquid; and a first supply pipe (L 5) that connects the first tray portion and the liquid dispersion portion to supply the absorbing liquid stored in the first tray portion to the liquid dispersion portion, characterized in that the first supply pipe (L 5) includes a heating portion that is configured to obtain a thermosiphon effect by heating the absorbing liquid and by partially vaporizing the absorbing liquid such that the first supply pipe (L 5) is configured to circulate the absorbing liquid using a density difference between the absorbing liquid flowing before the heating portion and the absorbing liquid flowing after the heating portion as a driving force, wherein the first supply pipe (L 5) does not have a pumping device that pumps the absorbing liquid or a control portion that controls a flow rate of the absorbing liquid, the liquid dispersion portion is positioned lower than a connecting portion with which the first supply pipe (L 5) and the first tray portion are connected, and the first supply pipe (L 5) or the heating portion partially includes a portion disposed higher than an extraction position of the absorbing liquid from the first regeneration portion, and the first supply pipe has a further portion in which the absorbing liquid flows after exiting the heating portion; said further portion being disposed higher than the heating portion.