This paper describes the optical characteristics of the Monoolein-PVC membrane in five basic taste solutions such as NaCl (salty), HCl (sour), Saccharose (sweet), Quinine hydrochloride (bitter) and mono-Sodium L-glutamate (umami). The Monoolein-PVC membrane was composed of poly(vinyl chloride) and a synthetic lipid, Monoolein. The optical characteristics of the membrane for the taste solutions could be measured quantitatively as an intensity variation of transmitted light of the membrane, using an optical measurement system with optical fiber. Since the optical intensity of transmitted light increased with different patterns for each taste solution, the membrane is supposed to have an optical selectivity. However, the optical characteristics of the membrane such as detection-threshold and dynamic-range did not agree with human taste characteristic. In order to improve the optical characteristics of the membrane, cholesterol or plasticizer was mixed into the membrane. As a result, the optical characteristics become closer to human characteristics in a few taste solutions. By taking advantage of these optical characteristics, some new usages, optical taste sensors and so on, are expected in the field of ion sensing materials.