Methyl 2-hydroxy-4-methylthiobutanoate and formamide are produced by means of reacting 2-hydroxy-4-methylthiobutanamide obtained by hydration of 2-hydroxy-4-methylthiobutyronitrile with methyl formate. Said methyl 2-hydroxy-4-methylthiobutanoate is hydrolyzed to give 2-hydroxy-4-methylthiobutanoic acid and methanol. No sulfuric acid is employed as a reacting agent, hence exhaustion of a large quantity of ammonium sulfate is prevented. Formamide and methanol thus produced can be recycled as reactants.