[Problem] To provide a system for recovering carbon dioxide from flue gas, in which a reboiler in a regenerator can be compactly installed, and a method therefor, in facilities where CO2 or the like contained in flue gas is recovered.[Solving Means] To include an absorber 1006 that absorbs CO2 contained in flue gas 1002, a regenerator 1008 that strips CO2 from CO2 absorbent (rich solution) 1007 to regenerate absorbent, internal shells 101 provided at a bottom of the regenerator 1008 with a predetermined interval therebetween, into which regenerated CO2 absorbent is introduced by a feeding unit 102 from a bottom side thereof so that the CO2 absorbent overflows from an upper end of the internal shell thereof toward the bottom of the regenerator, and a reboiler that is inserted into the internal shells 101 in a direction orthogonal to a vertical axis and includes a heat-transfer tube 103 that reboils absorbent. Steam separated from CO2 absorbent reboiled by the heat-transfer tube 103 is transferred to an upper part of a regenerator, condensed absorbent is caused to overflow from an upper end of the internal shell and to be discharged from a bottom side of a regenerator, and the absorbent is fed to the absorber 1006 as regenerated CO2 absorbent (lean solution) 1009.