This paper describes a measurement method for the amount of fibrosis in rat liver by fractal dimensions of the power spectrum shape. Some of the biotissues can be assumed to be an aggregation of point scatterers, and the spatial distribution of them (such as mean spacing or irregularity) may be used to obtain important information on tissue characterization. The power spectra of the scattering ultrasonic wave from random media are strongly affected by the spatial distribution of the scatterers. It was reported that the fractal dimension was one of the tools suitable for analyzing complex figures such as the power spectrum, and that the fractal dimension was sensitive to the spatial distribution of the scatterers. It was found that the amount of fibrosis generated artificially in the rat liver can be estimated quantitatively by the fractal dimension of the power spectrum shape. An attempt has been made to apply this method for ultrasonic measurements of the amount of fibrosis in the human liver.