Provided are a reclaimer 51 that introduces a part of an absorbent 17 that has absorbed CO 2 or H 2 S in a flue gas through an introduction line L 11 and stores the absorbent 17, a heating section 53 that heats the absorbent 17 stored in the reclaimer 51 to obtain recovered vapor 52, and a mixing tank 55 disposed on the introduction line L n through which the absorbent 17 is introduced into the reclaimer 51, and which introduces an absorbent (lean solution 17a) and an alkaline agent 54 for mixing thereof.