In the process for producing methionine of the present invention uses, as an equipment material for a step of hydrolyzing 5-(.beta.-methylmercaptoethyl)hydantoin in the presence of potassium carbonate to produce methionine, a stainless steel containing 21.0 to 30.0% by weight of a Cr element, 2.5 to 11.0% by weight of a Ni element and 1.0 to 5.0% by weight of a Mo element, a ratio of the total content of the Cr element and the Mo element to the content of the Ni element being from 4.7 to 14.0, is used.