Polydimethylsiloxane (PDMS) membranes were improved by graft polymerization of fluoroalkyl methacrylates (FALMA) and alkyl methacrylates (AMA) by electron beam, and the effect of the solubility and diffusibility of a monomer on graft polymerization and the pervaporation through grafted membrane were investigated. The difference of the grafted amount was small for the monomers with various solubility parameters and log P-ow which is the logarithm of the octanol-water partition coefficient. Compared to each other in the same group of FALMA or AMA, the sorpted and grafted amount for a monomer that has low molecular volume was high, and the sorpted and grafted amount for a monomer that has high molecular volume was low. FALMA-grafted PDMS membranes showed high separation performance compared to PDMS membranes. Among them, 2,2,3,3,3-pentafluoropropyl methacrylate grafted PDMS membrane, which had a high grafted amount, and F/Si calculated by the grafted amount had high selectivity for trichloroethylene (TCE). The FALMA-grafted PDMS membranes that had the high TCE concentrations in the sorbed solution exhibited high permselectivity for TCE.