The present invention provides a low-toxic and high-recovery industrial process for synthesizing an optically active diamine derivative represented by formula (D), the process comprising the steps of: (a) mixing a compound represented by formula (A) and a compound represented by formula (C) in organic solvents and secondary amine; (b) reaction under heating; (c) cooling and adding water to the mixed solution, allowing it to crystallize to obtain the compound represented by formula (D).