Using ultrasound frame data generated from the ultrasound echo reflected from the living tissue, the movement amount of the living tissue and its representative value are calculated (step 12). In a case where the representative value of the tissue movement amount is equal to or greater than a threshold value (YES in step 13), a hue conversion LUT_Large having a large degree of hue change is used, and an elastic image in which distortion is expressed by hue corresponding to the magnitude is generated (steps 14, 16, 17, and 18). On the other hand, in a case where the representative value of the movement amount of the living tissue is less than the predetermined threshold value (NO in step 13), a hue conversion LUT_small having a small degree of hue change is used to generate an elastic image (steps 15, 16, 17, and 18).
