An ultrasonic diagnostic apparatus according to the present invention includes: an ultrasonic signal processing section, which performs transmission processing for transmitting an ultrasonic wave toward a subject's blood vessel by driving a probe and reception processing for generating a received signal based on the ultrasonic wave reflected from the subject's blood vessel and received at the probe; a tomographic image processing section, which generates a tomographic image based on the received signal; a boundary detecting section, which detects the lumen-intima and media-adventitia boundaries of the blood vessel based on the received signal or the tomographic image; a vascular wall thickness calculating section, which calculates, as a vascular wall thickness value, the interval between the lumen-intima and media-adventitia boundaries detected by the boundary detecting section; a reliability determining section, which determines the reliability of the vascular wall thickness value by a signal feature of the received signal or an image information feature of the tomographic image at a location on the lumen-intima and/or media-adventitia boundaries detected; and a control section, which decides, in accordance with the decision made by the reliability determining section, that the vascular wall thickness value be defined as an intima-media thickness.