An ultrasonic diagnostic apparatus according to the present invention includes: a transmitting section 14 for driving an ultrasonic probe 13 sending out an ultrasonic transmitted wave toward a tissue of an organism; a receiving section 15 for receiving an ultrasonic reflected wave, produced by getting the ultrasonic transmitted wave reflected by the tissue of the organism, through the ultrasonic probe to generate a received signal; a phase detecting section 17 for detecting the phase of the received signal to generate a phase detected signal; a positional displacement calculating section 31a for calculating the magnitudes of positional displacements at multiple measuring points, set on the tissue of the organism, based on the phase detected signal; a thickness variation calculating section 31b for calculating thicknesses or thickness variations, each measured between two arbitrary points set with respect to the measuring points, based on the magnitudes of positional displacements; and a maximum/minimum value calculating section 31c for finding the maximum and minimum thicknesses or thickness variations during a maximum value finding period and a minimum value finding period, which are defined as respective partial periods of one cardiac cycle of the organism. At least one of the greatest thickness difference, strain and elastic property is calculated based on a difference between the maximum and minimum thicknesses or thickness variations.