The new supported liquid membranes (SLMs) were fabricated from ternary polymer solution contained ionic liquid in which primary and secondary phase separations were induced by the solvent evaporaton. The used ionic liquid and polymer matrix were BMIBF₄ (BMI+=1-(1-butyl)-3-methylimidazolium, BF₄=tetra-fluoro borate) and polyvinylidene fluoride (PVDF). Gas permeation properties of the SLM to O₂, N₂, and CO₂ were studied at various operating conditions. Although the SLM were operated under severe operating condition, it maintained high CO₂ permeability and selectivity for quite long time. The solubility coefficient of CO₂ in the membrane was very high in comparison with those of other gases, whereas there was no big difference in the diffusivity between CO₂ and other gases. Moreover, in the permeation of pure gases, it is observed that the ionic liquid content in the membrane affected the solubility of CO₂ in the membrane. With increasing ionic liquid content in the membrane, the permeability and selectivity of CO₂ increase significantly. Therefore, in the permeation of gases through SLM, the overall permeation performances were affected mainly by solubility coefficient. This observation can be discussed in terms of the influence of solubility coefficient with ionic liquid content in the membrane.