In this communication, we will report our recent results on the mechanism of selective permeation of steam and methanol from gas mixtures through ZSM-5 membrane. ZSM-5 membrane was prepared on the outer surface of a porous alpha-alumina tubular support by a secondary-growth method. Based on the results of structural characterization using FE-SEM, TEM, etc., ZSM-5 crystals tightly connected with each other in the absence of amorphous phase. ZSM-5 membrane was highly selective to steam and methanol, and hydrogen was retained in the permeation side at temperatures ranging from 150 to 300°C. Permeation and adsorption experimental results suggested that strong adsorption of water and methanol on Na cation occluded in the micropore of ZSM-5 contributed to the appearance of selective permeation. Such separation properties would be promising for membrane extractor in reactions such as Fischer-Tropsch synthesis and methanol synthesis.