An ultrasound diagnostic device for measuring a carotid artery wall property includes a transmission-reception processor, a transverse cross-sectional image generator, a transverse cross-sectional image selector, and a relative angle calculator. The transmission-reception processor performs transmission and reception processing of ultrasound with respect to the carotid artery. The transverse cross-sectional image generator generates transverse cross-sectional images based on reception signals for carotid artery cross-sections at different positions. Each generated image depicts a carotid artery transverse cross-section perpendicular to a longitudinal direction. The transverse cross-sectional image selector selects a specific image among the generated images that depicts ICA and ECA cross-sections. The relative angle calculator calculates relative angle of the ultrasound probe with respect to the carotid artery in a plane parallel to the carotid artery transverse cross-section, based on coordinates of the ICA and ECA cross-sections in the specific image.
