The present invention relates to a process for producing amino acid derivatives such as optically active .beta.-amino acid in short steps with good yield and high optical purity, which comprises reacting a keto acid of the formula (1): ##STR00001## wherein R.sup.1 is hydrogen, an optionally substituted hydrocarbon, etc.; R.sup.2 is a spacer; and R.sup.3 is an optionally substituted alkoxy, etc., or a salt thereof, with ammonia or an amine or a salt thereof in the presence of a chiral catalyst and in the presence or absence of an acid and/or a fluorine-containing alcohol, to give an amino acid derivative of the formula (2): ##STR00002## wherein Q is a group formed by removing one hydrogen atom from ammonia or an amine; X' is an acid and/or a fluorine-containing alcohol; and b is 0 or 1.