To uniformly extract a secondary flow based on quantitative calculation even in a complicated blood flow in a heart chamber or a blood vessel. There is provided a secondary flow detection device, including: a degree-of-swirl map calculation unit that obtains a velocity vector map calculated based on an echo signal reflected by an inspection target, calculates, as a value indicating a degree of a spatial change of a velocity vector, a degree of swirl based on the velocity vector map, and calculates, as a degree-of-swirl map, a spatial distribution of an iso-degree-of-swirl line obtained by connecting the degree of swirl of an equal value； a secondary flow candidate extraction unit that extracts, as a secondary flow candidate, an iso-degree-of-swirl line satisfying a predetermined condition among the iso-degree-of-swirl line indicated in the degree-of-swirl map； a feature amount calculation unit that calculates a feature amount of the velocity vector inside the secondary flow candidate； a secondary flow determination unit that determines whether the secondary flow candidate is a desired secondary flow based on the feature amount； and a secondary flow extraction unit that extracts and outputs the secondary flow determined by the secondary flow determination unit.
