A new method of Raman spectroscopy to measure strain of Raman-inactive materials deposited with Raman-active thin films was proposed. This method is denoted as the Raman Coating Method. This is the application of Raman spectroscopy, in which thin films of PbO are deposited on the surface of resins and metals using physical vapor deposition (PVD) as the pretreatment to measure strain. The relation between peak shift of PbO thin films and tensile strain was experimentally examined. This relation was independent of the mechanical properties of materials on which PbO thin films were deposited. The residual stress in PbO thin films was also measured. The absolute values of residual stress in the films on resins were much greater than those on metals. As an application of the proposed method, the tensile strain in carbon fiber of carbon fiber reinforced plastics (CFRP) was measured by Raman spectroscopy.