An ultrasound diagnostic apparatus includes an ultrasound image acquirer, an evaluation target determiner, a disease progression score calculator, a selector, and a display controller. The ultrasound image acquirer acquires ultrasound image signals of a plurality of frames. The evaluation target determiner analyzes the ultrasound image signal of each frame and determines the frame to be an evaluation target frame when the ultrasound image signal includes a target image section depicting a joint. The disease progression score calculator calculates, for each evaluation target frame, a disease progression score quantifying disease activity using an ultrasound image signal of the target image section included in the ultrasound image signal of the evaluation target frame. The selector selects at least one disease progression score in accordance with a predetermined numerical process. The display controller controls the display to display the selected disease progression score and an ultrasound image of a corresponding frame.
