The present invention relates to a production method capable of producing an optically active α-hydroxyphosphonic acid and its derivatives with sufficiently high enantioselectivity not only for aromatic aldehydes but also for aliphatic aldehydes, and more specifically to a method of producing an optically active α-hydroxyphosphonic acid and its derivatives, characterized in that an optically active aluminum(salalen) complex represented by any one of the following formulae (I), (I′), (II) and (II′): [wherein R1s are each alkyl group or aryl group independently; R2s are each alkyl group or aryl group independently; R3s are each alkyl group or aryl group independently, and two R3s may bond with each other to form a ring; R4s are each hydrogen atom, halogen atom, alkyl group, alkoxy group, nitro group, or cyano group independently; R5 is alkyl group; and X1 is halogen atom, alkyl group, alkoxy group, acetoxy group or toluenesulfonyloxy group] is used as a catalyst to asymmetrically hydrophosphonylate an aldehyde with phosphonic acid or its derivatives.