Transport mechanism of ethanol/water mixtures by pervaporation and vapor permeation through silicalite membrane was investigated. The activities of both ethanol and water in feed were controlled independently by vapor permeation to study the feed composition effects quantitatively. Also, adsorption experiments of single component and binary mixtures were carried out to measure the adsorbed mixture composition in the silicalite membrane. Ethanol permeance was independent of water concentration in feed. Water permeance, however, seriously decreased by the presence of ethanol in feed, and water permeation was restricted by ethanol The adsorption-diffusion model was considered for the transport mechanism through the silicalite membrane. Ethanol selectively adsorbed to silicalite membrane from ethanol/water vapor. The diffusion coefficients of water and ethanol were calculated based on the adsorption-diffusion model, and the results showed almost the same diffusivity between the single component and mixture feed case. Thus, high ethanol selective permeation through the silicalite membrane was explained by the ethanol selective adsorption to the silicalite membrane.