An ultrasonic diagnostic apparatus includes: a transmitting section for driving an ultrasonic probe sending out an ultrasonic transmitted wave toward a body tissue of an organism; a receiving section for receiving an ultrasonic reflected wave, produced by getting the transmitted wave reflected by the body tissue, through the probe; a phase detecting section for detecting the phase of the reflected wave; and a computing section for calculating the magnitudes of positional displacement at multiple measuring points on the body tissue based on a signal obtained by the detecting section and calculating the greatest thickness difference between two of the measuring points and/or an elastic property based on the magnitudes of positional displacement. The computing section calculates the maximum and minimum thicknesses or thickness variations between the two points based on the magnitudes of positional displacement at the two points during a part of one cardiac cycle, and calculates the greatest thickness difference and/or elastic property as the difference between the maximum and minimum values.