1. An ultrasonic diagnostic equipment, comprising: a memory configured to store a first contrast image generated by scanning an object with ultrasonic beams before stressing the object, and a second contrast image generated by scanning the object with ultrasonic beams after the stressing; and an arithmetic circuit configured to operationally connect to the image memory and to calculate an index value indicating an effect caused by the stressing, by using intensities of the first and second contrast images.