The carotid artery plaque properties are quantitatively determined by a carotid artery echo whereby predicting incidence of cerebral infarction or myocardial infarct. A method includes obtaining, coloring, and displaying steps. In the obtaining step, the integrated amounts per unit time of echo signals corresponding to pixels of an echo image of carotid artery plaque are obtained. The signals are obtained when the image is obtained by an IBS method. In the coloring step, the relationship between ranges and colors is referenced. The available full range of the integrated amount is previously divided into the ranges. The colors are assigned to the ranges. The pixels are classified into the ranges in accordance with the integrated amounts corresponding to the pixels. The pixels of the image are colored in colors corresponding to the ranges of the pixels. In the displaying step, the colored echo image is displayed on a display portion 30.
