In order to obtain higher membrane performance in the concentration of aqueous ethanol solutions, a porous poly(dimethylsiloxane) (PDMS) membrane was applied to the temperature-difference controlling evapomeation (TDEV) method. Characteristics of permeation and separation for aqueous ethanol solutions through a porous PDMS membrane during TDEV under various conditions are discussed from the viewpoint of membrane structure. When the characteristics of permeation and separation of a porous PDMS membrane were compared with those of a dense PDMS membrane, the ethanol/water selectivity of these membranes was almost equal, but the permeation rate of a porous PDMS membrane was higher by three orders of magnitude than that of a dense PDMS membrane. When the temperature of the feed solution was kept constant at 40 degrees C and the the temperature of the membrane surroundings was changed in TDEV, with dropping temperature of the membrane surroundings the permeation rate decreased but the ethanol/water selectivity increased for an aqueous solution of 10 wt% ethanol through a porous PDMS membrane.