PURPOSE: To obtain a carbamic acid ester, by reacting an amine or an amino acid with carbon monoxide, a hydroxyl-containing compound and oxygen in the presence of a catalyst and reutilizing the catalyst in the form of a solution without separating the catalyst from the reaction mother liquor as a solid.

CONSTITUTION: The objective compound can be produced by reacting an amine or an amino acid with carbon monoxide, a hydroxyl-containing compound (e.g. alcohol) and oxygen in the presence of a catalyst consisting of a group VIII platinum-group transition metal of the periodic table or its salt, a complex of a cuprous salt, a Ti(III) salt or a vanadium salt and a basic compound (e.g. sulfolane). The separation efficiency of the carbamic acid ester and the solvent can be improved by leaving a proper amount of amine or amino acid in or adding the amine, etc., to the mother liquor in the separation of the product from the reaction liquid by distillation.