Abstract: A process for preparing a porous ceramic membrane to be employed for separating condensible gases and so on, which process comprises disposing on a porous ceramic substrate a layer of alumina sol formed by hydrolyzing an alcoholate or a chelate of aluminum, with subsequent drying and burning thereof, impregnating the resulting burnt body with a solution of an alcoholate or a chelate of aluminum in an organic solvent and subjecting then the aluminum alcoholate or chelate soaked in the burnt body to hydrolysis in a heated steam to cause conversion thereof into alumina sol, immersing the so treated body in an aqueous solution of sodium silicate, followed by, a heat treatment thereof in steam, after the body has been removed from the solution repeating the foregoing procedures until the capillary pores in the substrate would have sufficiently been filled by the alumina sol, immersing the so treated body finally in an aqeous solution of sodium silicate, followed by, a further heat treatment thereof in a steam afte