PURPOSE: To specifically obtain an L-α-amino acid useful as a raw material for food additives, medicines, cosmetics, feeds, etc.. by reacting an L-α-amino acid derivative with a β-ureidopropionase.

CONSTITUTION: This method for producing an L-α-amino acid of formula II (R1 is phenyl, an alkyl, thienyl, etc.) is to react an L-α-amino acid derivative of formula I (R2 is carbamyl, formyl or acetyl) with a β-ureidopropionase in an aqueous medium, produce the L-α-amino acid of formula II and isolate the L-a-amino acid by concentrating, neutralizing. ion exchange resin treatment, etc. The β-ureidopropionase is produced by Pseudomonas striata (IFO12996), etc.