An ultrasonic diagnostic device according to an embodiment comprises: a setting unit (32a) which sets a range gate and a region of interest that includes the range gate therein a color Doppler information acquisition unit which acquires color Doppler information on the basis of a received signal from a subject corresponding to the region of interest and a region changing unit (32c) which enlarges the region of interest so as to include the range gate therein in response to the range gate moving toward the outside of the region of interest.
