A fatty tissue image display device includes a light source, an ultrasonic wave transmission/reception mechanism, an analysis unit which calculates a velocity change of ultrasonic waves after irradiation with a heating beam as compared to before irradiation with light, a display control unit which displays the distribution of the calculated velocity change of the ultrasonic waves, a designation unit which waits for the designation of a region of interest, a histogram calculation unit which, based on luminance information or color information within the designated region of interest, calculates the histograms of a fatty region showing a negative velocity change of the ultrasonic waves and a normal region showing a positive velocity change of the ultrasonic waves, and an index calculation unit which, from the calculated histograms of the fatty and normal regions, calculates a fatty change index that is an index of a proportion of fatty tissue.