An ultrasound diagnostic apparatus according to an embodiment includes processing circuitry. The processing circuitry is configured to obtain the position of the boundary of a region of interest that is set in first ultrasound image data of a subject. The processing circuitry is configured to generate second ultrasound image data by assigning a pixel value to each of pixels of which a change of the brightness value between before and after a contrast enhancement is equal to or larger than a threshold value with regard to pre-contrast-enhanced image data and post-contrast-enhanced image data of the subject both of which were acquired after a treatment using a puncture needle has been performed, the assigned pixel value corresponding to the distance between the pixel and the boundary of the region of interest. The processing circuitry is configured to cause a display unit to display the second ultrasound image data.
