An X-ray diagnostic apparatus according to the embodiment includes an X-ray tube, an X-ray detector, image generating unit generating time-series medical images of vasoganglion in a predetermined organ of a subject, region setting unit setting a first upstream and downstream region of a stenosis location in a first blood vessel in the vasoganglion on the medical images, curve generating unit generating a stenosis upstream and downstream curve indicating a change in pixel value in the time-series based on pixel values included in the first upstream and downstream region respectively, stenosis index generating unit generating a stenosis index indicating the degree of stenosis in the first blood vessel based on the stenosis upstream and downstream curve, and display unit displaying the stenosis index.