An optically-active bis(alkynylphosphino)ethane-borane derivative represented by formula (1): ##STR00001## wherein R.sup.1 and R.sup.2, which may be the same or different, each represent an alkyl group, a phenyl group, an alkylsilyl group or a hydrogen atom; R.sup.3 represents a branched alkyl group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group; and the asterisk * indicates an optically-active site. The derivative (1) is prepared by bromination of, e.g., an (S)-t-butylmethylphosphine-borane, reaction with an alkynyl lithium, deprotonation, followed by oxidative coupling. Deprotection of the derivative (1) by deboranation gives an optically-active bis(alkynylphosphino)ethane derivative useful as a ligand providing an asymmetric catalyst for catalytic asymmetric synthesis. The asymmetric catalyst having the ligand exhibits high selectivity and catalyst activity.