PURPOSE: To obtain an inorganic permeation membrane excellent in separation performance and permeation velocity by concentrating an orthosilicic ester soln. in the superfine through-holes of porous glass and thereafter introducing a gelling raw material soln. to produce hydrated silica-alumina gel and furthermore performing hydrothermal reaction.

CONSTITUTION: A silica source is concentrated at high density in the super-fine through-hole paths of porous glass by such a method that porous glass is immersed in a silicic acid ester soln. controlled to required concn. and this silicic acid ester soln. is concentrated in the superfine through-hole paths. Then the aq. solns. of sodium compd. and aluminum compd. are fed to produce hydrated silica-alumina gel in the superfine through-hole paths. Furthermore hydrothermal reaction is performed while bringing one end side into contact with water or a dilute alkaline aq. soln. and also bringing the other end side into contact with air or inert gas and the hydrated silica-alumina gel is treated with a cationic aq. soln. by requirement. The inorganic permeation membrane having a zeolite layer obtained thereby shows stable performance in dehumidification, concentration of fluid and removal of trace impurities at high temp. not lower than 100°C.