1. An ultrasonic diagnostic apparatus comprising: an input unit to which at least two ROIs (Region of Interest(s)) are input; a calculating unit that calculates strain values of tissue with respect to the at least two ROIs by applying a pressure onto an object; and a display unit configured to display on a single screen an image in colors depending on the strain values of the at least two ROIs with a corresponding strain value/time graph for each of the at least two ROIs.