An ultrasound diagnostic apparatus according to the present invention includes: a three-dimensional data generation unit (105) which generates three-dimensional data for each region in the body of a subject based on reflected waves reflecting back from the body of the subject after ultrasound waves have been transmitted towards the body of the subject a measurement image selection unit (106a) which respectively selects, for each region, one of the two-dimensional cross-sections that compose the three-dimensional data, as a measurement reference image used for measuring a length of each region in the body of the subject a measurement and calculation unit (112) which measures a length of each region in the body of the subject using the respectively selected measurement reference image, and calculates an estimated weight of the subject using the measured lengths and a display unit (111) which outputs the estimated weight thus calculated.
