We have ever developed micro dialysis system that consists of micro channels and polyethersulfone (PES) membranes. However, when blood was used in dialysis experiments, platelets adhered to the surface of membrane and performance of the membrane degraded. Therefore, we modify the surface of PES membranes by coating fluorinated diamond-like carbon (F-DLC). We examined antithrombogencity of the F-DLC/PES membranes using a microfluidic device and experimentally found that F-DLC drastically reduced the amount of cells attached to the surface. We conducted long-term experiments for 1 week and the diffusion characteristics were found to retrogress because of fouling without the surface modification.