A transmission reception unit forms a transmission beam by outputting a transmission signal to each of a plurality of vibrating elements provided in a probe and further forms a reception beam on the basis of a plurality of wave reception signals obtained from the plurality of vibrating elements. Thus, an ultrasonic beam (transmission beam and reception beam) is scanned in a scan surface. A velocity vector computation unit forms a two-dimensional velocity vector distribution in the scan surface from information regarding velocity of blood flow in an ultrasonic beam direction. A vortex detection unit tracks a flow of a fluid on the basis of the two-dimensional velocity vector distribution obtained by the velocity vector computation unit and detects a vortex in the fluid on the basis of whether or not the flow of the fluid satisfies a recurrence condition.
