Poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) which have strong affinity for benzene were selected as membrane materials and the characteristics of permeation and separation for the benzene/cyclohexane mixtures through these poly(alkyl methacrylate) cross-linked with ethylene glycol dimethacrylate (EGDM) membranes by pervaporation were investigated. The cross-linked poly(alkyl methacrylate) membranes exhibited a benzene permselectivity for the benzene/cyclohexane mixtures and the permeation rate increased with increasing benzene in the feed solution. The permselectivity of their membranes was strongly governed by the diffusion separation process depending on the difference of the molecular size between the benzene molecule and the cyclohexane molecule. The depression of swelling of those membranes with the increase of the cross-linker content in the benzene/cyclohexane mixtures enhanced the benzene permselectivity. This result was attributed to the increase of the selectivity in the sorption separation process with the depression of swelling of the membrane. Furthermore, the cross-linked copolymer (PMMA-PEMA-EGDM) membranes showed excellent benzene permselectivity. These results suggested that both, the increase of affinity of the membrane for benzene and depression of swelling of the membrane, were very important in the separation of the benzene/cyclohexane mixtures.