The invention relates to an industrially advantageous method for producing an optically active 1,2-bis(dialkylphosphino)benzene derivative, wherein borane is removed from a phosphine-borane compound (1), followed by lithiation, then the reaction product is reacted with an alkyldihalogenophosphine represented by RaPX'2, and thereafter the reaction product is reacted with a Grignard reagent represented by RbMgX", whereby an optically active 1,2-bis(dialkylphosphino)benzene derivative (A) is produced. R1 and R2 each represent an alkyl group having 1 to 8 carbon atoms, and the number of carbon atoms is different between R1 and R2. Ra is either R1 or R2 and Rb is the other of R1 and R2. X, X', and X" each represent a halogen atom.