1. An ultrasonic diagnostic apparatus comprising: a data acquisition unit configured to ultrasonically scan a two-dimensional region or a three-dimensional region as a region to be scanned which includes at least part of a heart of an object and acquire ultrasonic data associated with the region to be scanned; a temporal change curve acquisition unit configured to acquire temporal change curves of a wall motion parameter associated with a plurality of regions of the heart by using the ultrasonic data associated with the region to be scanned; an index value acquisition unit configured to acquire an index value associated with cardiac wall motion by calculating a difference value of the wall motion parameter of two arbitrary regions, of the plurality of regions of the heart, at each phase in an analysis period by using temporal change curves associated with the two arbitrary regions, calculating a total sum of the difference values in the analysis period, and normalizing the total sum with a predetermined value; and a display unit configured to display the index value in a predetermined form.