PURPOSE: To attain excellent recovering performance in selectively recovering a gaseous component rich in H2S by concentrating H2S in a liquid phase with heating and pressure lowering in a concentrating tower.

CONSTITUTION: A partial stream of a regenerated detergent is introduced into the top part of a concentrating tower 9 through a conduit 10 after being expanded 42. The detergent is heated 41 between a returned material washing region in the upper range of the concentrating tower 9 and a feeding port 8 of the detergent loaded from a washing tower 2. Concentration of H2S is carried out in a liquid phase in a concentrating region located in a part lower than the feeding port 8 of the detergent. The loaded and concentrated detergent is extracted from the bottom of the concentrating tower 9 through a conduit 11. In this process, a partial stream of the detergent from the conduit 11 passes a conduit 12, is heated in a reboiler 13 and is returned to the concentrating tower 9 passing a conduit 14 while part of the detergent is vaporized. A residual gas stream from the concentrating tower is extracted from the top part of the concentrating tower 9 through a conduit 15. The detergent which is not returned into the concentrating tower 9 is introduced into a regeneration tower 17 and liberated from a dissolved acidic gas by high temperature regeneration.