To remove hydrogen sulfide in a short time in high productivity from a sulfurized oil and fat or a sulfurized fatty acid alkyl ester useful as a sulfur- based extreme-pressure agent for metal working oil by passing a specific gas through the sulfur-containing compound.

(A) A sulfurized oil and fat such as sulfurized lard or a sulfurized fatty acid alkyl ester such as a sulfurized oleic acid methyl ester is purified by passing (B) a gas having an oxygen content of 30-100vol.% under a pressure between normal pressure and 0.5kg/cm2 at 70-120°C or passing (C) air under a pressure of 2-5kg/cm2 at 70-120°C. The above process is carried out preferably in the presence of a desulfation catalyst {e.g. produced by supporting basic cupric carbonate [CuCO3.Cu(OH)2] on an activated carbon carrier}.