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. In a case where the representative value of the tissue movement amount is equal to or greater than a threshold value, 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. 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, a hue conversion LUT_small having a small degree of hue change is used to generate an elastic image.
