To provide a catalyst useful for an asymmetric hydrogen-transfer reducing reaction capable of obtaining a sulfonate containing a by-product obtained by an industrial production method as a ligand.

A ruthenium catalyst composition comprises 0.1-20 wt.% N,N'- disulfonyl-1,2-diamines represented by the general formula 1 (wherein R1 and R2 are each independently 1-12C alkyl or aryl group, and may be bonded to each other to form a ring; R3 is ≤20C alkyl or aryl group; and (*) is an asymmetric carbon atom), and 99.9-80 wt.% ruthenium complex represented by the general formula 2 (wherein R1, R2, and R3 are synonymous with those of the general formula 1; X is a halogen atom; Ar is an aryl group; and (*) is an asymmetric carbon atom).