A CO2 recovering apparatus includes: a CO2 absorber that brings flue gas containing CO2 into contact with CO2 absorbent to reduce the CO2 contained in the flue gas; a regenerator that reduces CO2 contained in rich solvent that has absorbed CO2 in the CO2 absorber to regenerate the rich solvent, so that the CO2 absorbent that is lean solvent having CO2 reduced in the regenerator is reused in the CO2 absorber; and a controller that controls to detect the absorbent concentration in the CO2 absorbent, to increase the volume of CO2 absorbent to be circulated based on a decrease in the absorbent concentration, and to adjust the volume of steam to be supplied in the regenerator based on the volume of the CO2 absorbent to be circulated.