An ultrasonic diagnostic apparatus transmits an ultrasonic wave toward a body and obtains biological information based on an echo signal received and includes: an intensity distribution generating section that generates an echo intensity distribution in a depth direction about a vascular wall based on the echo signal; a template generating section that generates a template to detect a boundary based on template data provided in advance to represent a reference pattern of the intensity distribution; a pattern similarity calculating section that changes the depth and intima-media thickness pattern of the template to calculate similarity between the template and the intensity distribution on any change made; and a boundary defining section that defines lumen and adventitia boundaries based on the degree of similarity calculated on any change made. The intima-media thickness is thus determined without depending on the magnitudes of echo intensity variations on the lumen and adventitia sides.