The present invention provides a water-soluble transition metal-diamine complex which can be easily separated from reaction products through liquid separation, etc. and is recycleable; an optically active diamine compound constituting the ligand of the complex; and a catalyst for asymmetric synthesis which comprises these. The present invention relates to a water-soluble optically active transition metal-diamine complex represented by the formula (2): [wherein R1 and R2 each represents hydrogen, a hydrocarbon group, —SO2R13 (wherein R13 is a hydrocarbon group, substituted amino, etc.), etc.; R3 to R12 each represents hydrogen, a hydrocarbon group, alkoxy, substituted amino, etc.; M represents a transition metal; X represents halogen; L represents a ligand; and * indicates an asymmetric carbon atom; provided that at least one of R3 to R7 and R8 to R12 is substituted amino], a catalyst for asymmetric synthesis containing the complex, and a process for producing an optically active alcohol, which comprises using the catalyst to asymmetrically reduce a ketone.