Disclosed are an ultrasound system of measuring a number of ribs of a fetus and a method thereof. The ultrasound system of measuring the number of ribs of the fetus in three dimensions may include a setting unit that is used by a user, to set a portion where the number of ribs is measured in an ultrasound image, as a region of interest (ROI), a measuring unit to measure the number of ribs in the set ROI by using an auto rib extracting algorithm, and a display unit to display the measured number of ribs.
