A CO 2 recovery system including an absorption tower that contacts CO 2 -containing gas with a CO 2 -absorbing solution to remove CO 2 and a regeneration tower that regenerates a rich solution having absorbed CO 2, and reusing a lean solution, obtained by removing CO 2 from the rich solution in the regeneration tower, in the absorption tower, comprising: a regeneration heater that extracts the lean solution recovered near a bottom portion of the regeneration tower to the outside, and heat-exchanges the lean solution with saturated steam; a rich-solution supply pipe for feeding the rich solution from the absorption tower; a first rich-solution supply pipe and a second rich-solution supply pipe which are branched from the rich-solution supply pipe, wherein the second rich-solution supply pipe is connected to the regeneration tower near an upper stage portion of the regeneration tower; a steam-condensate heat exchanger that heat-exchanges the first rich solution with steam condensate directly fed from the regeneration heater to the steam-condensate heat exchanger; wherein the steam-condensate heat exchanger is interposed in the first rich-solution supply pipe; a flash drum provided downstream of the steam-condensate heat-exchanger for removing a part of CO 2 from the first rich solution; a semi-lean-solution heat exchanger that is provided in the second rich-solution supply pipe, and heats the second rich solution with residual heat of a semi-lean solution obtained by removing the part of CO 2 from the first rich solution in the flash drum, wherein said semi-lean solution is supplied by a semi-lean-solution supply pipe wherein the end of the semi-lean-solution supply pipe is connected to a middle stage portion of the absorption tower; and a lean-solution heat exchanger that is interposed in the first rich-solution supply pipe at an upstream position relative to the steam-condensate heat exchanger, and heats the first rich solution with residual heat of a lean solution fed from the regeneration tower wherein the end of the lean solution supply pipe is connected to an upper stage portion of the absorption tower. a regeneration heater that extracts the lean solution recovered near a bottom portion of the regeneration tower to the outside, and heat-exchanges the lean solution with saturated steam; a rich-solution supply pipe for feeding the rich solution from the absorption tower; a first rich-solution supply pipe and a second rich-solution supply pipe which are branched from the rich-solution supply pipe, wherein the second rich-solution supply pipe is connected to the regeneration tower near an upper stage portion of the regeneration tower; a steam-condensate heat exchanger that heat-exchanges the first rich solution with steam condensate directly fed from the regeneration heater to the steam-condensate heat exchanger; wherein the steam-condensate heat exchanger is interposed in the first rich-solution supply pipe; a flash drum provided downstream of the steam-condensate heat-exchanger for removing a part of CO 2 from the first rich solution; a semi-lean-solution heat exchanger that is provided in the second rich-solution supply pipe, and heats the second rich solution with residual heat of a semi-lean solution obtained by removing the part of CO 2 from the first rich solution in the flash drum, wherein said semi-lean solution is supplied by a semi-lean-solution supply pipe wherein the end of the semi-lean-solution supply pipe is connected to a middle stage portion of the absorption tower; and a lean-solution heat exchanger that is interposed in the first rich-solution supply pipe at an upstream position relative to the steam-condensate heat exchanger, and heats the first rich solution with residual heat of a lean solution fed from the regeneration tower wherein the end of the lean solution supply pipe is connected to an upper stage portion of the absorption tower.