An object of the present invention is to provide an ultrasonic diagnostic apparatus and a method thereof having a highly-reliable elastic evaluation unit for tissues.The present invention is provided with a signal processing unit 23 that processes received data obtained after ultrasonic waves are transmitted and received to/from an inspection target through a probe 11. An ROI detection unit 21 of the processing unit 23 obtains a distance index indicating a region proper for an elastic evaluation on the basis of brightness distribution of the received data obtained by transmitting and receiving first ultrasonic waves to/from the probe 11, and sets an ROI on the basis of the value of the distance index. Then, second ultrasonic waves are transmitted to the ROI to generate shear waves. An elastic evaluation unit 22 calculates a shear wave velocity on the basis of the received data obtained by transmitting and receiving third ultrasonic waves in the ROI, and outputs the shear wave velocity and an elastic evaluation value of the ROI as a reliability index.
