In this study, the thickness for first layer of metal-resin double layer materials is measured using photothermal deflection method. While the modulated pump beam is irradiating on material, the periodic temperature distribution changes occur in the material due to photothermal effect. The periodic temperature distribution depends on the effective thermal diffusion coefficient in the range of thermal wave influence inside the material. According to the thickness for first layer, the effective thermal diffusion coefficient will be changed, which results in phase change of probe beam. Based on these phenomena, the profiles of phase change according to the various thickness for first layer for five-step of frequency were obtained using numerical analysis. Also, numerical results were non-dimensionalized. It can be identified that the phase profiles have the same tendency regardless of frequency changes if the dimensional parameter is identical. As a result, the thickness for first layer can be determined by the frequency of pump beam and the phase delay of probe beam.