To provide an ion exchange membrane for alkaline chloride electrolysis having a low electric resistance and further having a sufficient mechanical strength.To employ an ion exchange membrane containing a polymer having units (U1). Q1, Q2=a perfluoroalkylene group or the like; Rf1, Rf2=a perfluoroalkyl group or the like; X1=an oxygen atom or the like; a=0 or the like; Y1=a fluorine atom or the like; r=0 or 1; and M=a hydrogen atom or an alkali metal atom.