A bloodstream visualizing diagnostic apparatus capable of visualizing and displaying a value relating to energy efficiency of bloodstream measured for an actual patient, and capable of improving usability, is provided. Provided is an bloodstream visualizing diagnostic apparatus which acquires flow rate information of a bloodstream flowing through a blood vessel in the body, calculates an energy loss of the bloodstream at a plurality of representative points within a region of interest in the blood vessel, using a calculation formula which does not explicitly include a blood pressure in the blood vessel, on the basis of the acquired flow rate information, and generates an image showing a magnitude of the calculated energy loss at the plurality of representative points.
