Gas-phase hydration of ethylene over a porous H-ZSM-5 tube was investigated. Yield of C2H5OH is drastically increased by the porous H-ZSM-5 tube as a catalytic filter which has a function of catalyst and separator. The combination of the porous H-ZSM-5 tube with the powder H-ZSM-5 catalysts is effective for the synthesis of ethanol at high yield.