To achieve a higher S/N ratio and a higher sensitivity by making the thermal excitation wavelength in a permeable film match the absorption peak wavelength of a photoabsorption layer without being affected by the absorption of light, chemical changes, fluorescence and phosphorescence at the permeable film for the promotion of photothermal effect in a method of measuring the physical characteristics of the laminate sample having the permeable film on the surface thereof and the photoabsorption layer therein utilizing the photothermal effect obtained by irradiating the laminate sample with thermally excited light.

In the method of measuring the physical characteristics of the laminate sample having the permeable film on the surface thereof and the photoabsorption layer therein utilizing the photothermal effect obtained by irradiating it with the thermally excited light, when the absorption peak wavelength of the photoabsorption layer is λ1 and the refractive index of the permeable film n1, the wave length approximated by λ=λ1n1 50 nm is defined as the wavelength of a thermally excited light source.