[Problem] To provide an ion exchange membrane for vanadium redox batteries having excellent chemical durability and heat resistance, and low resistance, in which vanadium ion permeation is suppressed. [Solution] An ion exchange membrane for vanadium redox batteries characterized by containing a polymer containing a component having a sulfonic acid group as well as general formula (1), Wherein X represents a monovalent or divalent group that is a nitrile group, an amide group, an ester group, or a carboxyl group, Z represents an O atom or a S atom, and Ar' represents a divalent aromatic group.
