The pervaporation of IPA(isopropanol)-water mixture was carried out by using PDMS (poly(dimethylsiloxane))/ceramic composite membrane. In the pervaporation using homogeneous PDMS membrane without ceramic support selectivities of IPA were inversely proportional to operating temperature. However, selectivities of IPA in the pervaporation using PDMS/ceramic composite membrane increased with operating temperature in the range from 0 to 20 wt% of IPA in feed mixture. In this composition range, the effect of capillary condensation of water in ceramic pores on selectivities is more dominant than that of plasticization of PDMS by IPA. In more than 20 wt% IPA in feed mixtures the plasticization of PDMS by TPA in feed is dominant, thereby the selectivities of IPA is inversely proportional to the operating temperature. These coupling effects containing capillary condensation and plasticizing effect were investigated by measuring permeation ratio of each component. In the case of PDMS/ceramic composite membrane, fluctuation of permeation ratio with operating temperature was observed around 0-10% of IPA in feed mixture. It is explained by the blockage in ceramic pore due to capillary condensation of water. No severe fluctuation was observed at any feed concentration range by using homogeneous PDMS membrane without ceramic support.