A model gas separator that makes use of the molecular exchange flow through porous membrane of 18 cm2 area is fabricated. The effect of molecular exchange flow is accumulated by the counter flow of gas mixture that flows around the membrane. The half part of the device concentrates light molecules, and the other concentrates heavy molecules. This study demonstrates the capability of the device to make two flows of different gases whose difference of mole percentage is around 6.5% from a continuous feed flow of 3 sccm helium-neon 50% mixture. The effect of the product flow rate and the flow rate around the membrane are also investigated.