The t-butyl alcohol synthesis was carried out in a batch reactor and a polyphenylene oxide membrane reactor using concentrated aqueous 12-tungstophosphorc acid catalyst. The prepared aqueous catalyst solution n a batch reactor showed a good catalytic activity in the isobutene hydration reaction. The membrane reactor showed the better performance than the batch reactor under the same reaction conditions. In addition to this, the recovery of 12-tungstophosphoric acid was possible at the end of the reacton by using the nonporous polypenylene exide membrane in this membrane reactor.