Disclosed is a process for producing methionine, which comprises hydrolyzing 5-(β-methylmercaptoethyl)hydantoin using at least one potassium compound selected from potassium carbonate, potassium bicarbonate and potassium hydroxide, crystallizing the hydrolyzate under pressure of carbonic acid gas thereby separating and collecting methionine, and heat treating at least a portion of the resulting filtrate thereby recovering methionine dimer contained in the filtrate as methionine, the process being characterized by using, as a material of an equipment of a facility for recovery through a heat treatment, a ferritic stainless steel containing 17.0 to 32.0% by weight of Cr element of, 1.0 to 3.0% by weight of Mo element and 0.6% by weight or less of Ni element, or zirconium.