According to this invention, an ultrasound diagnostic apparatus is provided which generates a tomographic image of a subject site in a living body, including a region-of-interest setting section (33) which sets a region-of-interest in the tomographic image, a data acquiring section which samples, from one piece of sound ray data within the region-of-interest, pieces of data at at least two positions including a piece of data at one position included in the one piece of sound ray data and a piece of data at at least one position upwardly or downwardly spaced apart from the one position by an interval of a predetermined number of pixels in a depth direction of the one piece of sound ray data, and a blood flow data calculating section (35) which calculates a piece of blood flow data at the one position by performing spatial averaging (35d) on the pieces of data sampled by the data acquiring section.
