PROBLEM TO BE SOLVED: To prevent decline of capacity for adsorption that can be caused in resuming adsorption treatment after regeneration of adsorbent without causing increase in cost and time loss.SOLUTION: A regenerator of adsorbent 20 for adsorbing impurities contained in carbon dioxide comprises: regeneration gas supply means 23 for supplying regeneration gas to an adsorption tower 11 which is filled with the adsorbent; heating means 25 for heating the regeneration gas supplied to the adsorption tower 11; gas circulation means 27 for circulating the substitution gas supplied to the adsorption tower 11 along a circulation route 30 including the adsorption tower 11; cooling means 28 for cooling the substitution gas circulating along the circulation route 30; and control means 29 for making the substitution gas circulate while cooling along the circulation route 30 after heating and supplying the regeneration gas to the adsorption tower 11.
