A SUS316 substrate surface was modified with fluoroalkylsilane (FAS) by a chemical vapor reaction with the aim to form fluoride thin layers on the metal surface. The water repellency of the substrate surface increased with the reaction time. When the reaction temperature was 150ºC and the reaction time was over 1 hour, the water contact angle of the substrate surface reached 110º. Furthermore, a random multi layer formed when the reaction time increased and the reaction temperature was raised. The increasing the amount of FAS in the reaction stage reinforced the durability of this layer. And the layer that formed on the SUS316 substrate was stronger than that which formed on the glass. X-ray photoelectron spectra (XPS) analysis revealed C-F covalent bonds on the treated substrate. On the basis of these results, the formation mechanism of fluoride thin layers was discussed.