Methyl methacrylate-methacrylic acid copolymer (MMA-MAA) membranes ionically crosslinked with Fe3+ and Co2+ ions (MMA-MAA-Fe3+ and -Co2+) were prepared, and characteristics of permeation and separation for a benzene/cyclohexane mixture of 50 wt % benzene through these membranes in pervaporation (PV) were studied. Although the introduction of the metal ions to the MMA-MAA membrane enhanced both benzene permselectivity and permeability for a benzene/cyclohexane mixture, the PV characteristics between the MMA-MAA-Fe3+ and -Co2+ membranes were significantly different. The difference in the PV characteristics between these membranes was strongly governed by the difference of these membrane structures based on the glass transition temperature, contact angle to methylene iodide, degree of swelling, and mixture composition absorbed in the membrane, and so on.