A continuation of our previous study, the goal. of this study is to express the dispersion conditions of particles in a dispersed material as a fixed quantity, and to clarify their impact on thermal diffusivity. The test method used is the same as that for the previous report. For the study, the thermal diffusivity of a hulk sample was measure, and a test piece was taken from the sample. A microphotograph was taken of the test piece, which was put through an image analyzer. Using fractal dimensions F, we evaluate the dispersion conditions of the particles, and then investigated the relationship between the dispersion conditions and thermal diffusivity. Fractal dimensions F proved to be an effective parameter for expressing the dispersion conditions of the particle. As for the effects on thermal diffusivity, while changes in fractal dimensions F are a matter of course, the effect on thermal diffusivity is also large, depending on whether the ratio of the thermal diffusivity of the base material a(c) and the thermal diffusivity of the dispersed particles a(d) (a(d)*=a(c)/a(d)) is greater or less than 1.0.