a method for producing a desired optically active carboxylic acid with a high optical purity , wherein a complex catalyst used can be recovered and reused as an aqueous solution . the method contains the step of subjecting an & amp ; agr ;,& amp ; bgr ; - unsaturated carboxylic acid in water or a mixed solvent of water and a water - insoluble organic solvent in the presence of a sulfonated binap — ru complex represented by the formula : ? 2 # 191 - binap }] x wherein x represents a chlorine atom , a bromine atom or an iodine atom , arene represents a benzene or an alkyl - substituted benzene , m represents an alkaline metal atom , and binap represents 2 , 2 ′- bis - 1 , 1 ′- binaphthyl to an asymmetric hydrogenation . the sulfonated binap — ru complex can be recycled .