The present invention is to provide a method for producing the desired optically active .beta.-amino acid derivatives of high optical purities in high yields, without requiring a step of deprotection. More particularly, the present invention relates to a method for producing an optically active .beta.-amino acid derivative or a salt thereof represented by the formula (2): ##STR00001## which comprises reacting an .alpha.,.beta.-unsaturated carboxylic acid derivative or a salt thereof represented by the formula (1): ##STR00002## with an amines or a salt thereof in the presence of a chiral catalyst and in the presence or absence of an acid.