A dehydration process of ethanol solution usingpolyion complex (PIC) membrane by pervaporation was designed. A permeation equation with experimentally determined permeability was used to describe the permeate flux and separation factor under various operating conditions. Considering material and heat balances in a module using the equation, the effects of permeate side pressure and recycle operation on dehydratiion performance were evaluated. When 94 wt% ethanol solution was dehydrated up to 97 wt%, no significant effect on membrane area was observed under permeate side pressures of 13-666 Pa. When ethanol concentration in the feed solution was below 94 wt%, high permeate flux was obtained by a recycle operation. From the result of these examinations, dehydration of ethanol solution on a pilot-scale was performed. It was verified that the permeation equation could be applied for design of a dehydration process for ethanol solution. A dehydrated ethanol product could be stably obtained from 94 wt% ethanol solution using a PIC membrane over a long period.