Recovery of monoamino monocarboxylic and monoamino dicarboxylic acids from the some mixtures consisting of six kinds of amino acids in aqueous solutions was conducted in a batch system under 1.96 MPa·G at 30°C by taking advantage of Donnan exclusion of cellulose acetate membrane. The mixtures was adjusted to pH7. This method was especially effective for the recovery of monoamino dicarboxylic acids from the mixture of amino acids in concentration of each component about 0.001 mol dm^-3. Equations for the batch system were derived on the basis of material balance, and their application was examined. As a result, these equations were applicable to monoamino dicarboxylic acid, and not applicable to mono-amino monocarboxylic acid because of failure of material balance caused by adsorption by the membrane.