||Cell membrane permeability is one of the crucial parameters in the pharmaceutical industry when designing a new drug. Thus, various in vitro assays have been developed to estimate cell membrane permeability of the drug. Instead of a real cell membrane, many assays use an artificial membrane whose microscopic structures are usually unknown, requiring a more accurate and versatile technique. In this research, we developed a new platform to measure the permeability of drug molecules across a planar phospholipid bilayer with a well-defined area and structure. The entire system was constructed within a conventional UV spectrometer cell, and the transport of drug molecules across the bilayer was recorded by UV absorbance in real time. We obtained a much higher permeability compared to the other assays, and this is related to the thickness of the lipid bilayer. Also, we could observe the real-time permeability changes upon the addition of a membrane-disrupting surfactant.