PURPOSE: To efficiently remove org. sulfur compds. by absorbing and removing mainly CS2 in a first stage from a gas contg. CS2 and COS, then decomposing COS in a second stage, and absorbing in a third stage H2S generated in the second stage and removing it.

CONSTITUTION: After warming a gas 1 contg. org. S compds. such as COS, CS2, in a heating device 2, the gas is fed to a packed tower 3 contg. porous bodies impregnated with a secondary amine such as diethanolamine where CS2 is mainly absorbed and removed. Then, the gas is fed to a packed tower 5 contg. a catalyst prepd. by impregnating diglycolamine into alumina, zeolite, iron oxide, etc., and COS is decomposed there. H2S generated by the decomposition of COS is fed to a packed tower 6 contg. an absorbent comprising iron oxide, iron hydroxide, etc., and absorbed and removed, thereby producing purified gas 7.