An X-ray diagnostic apparatus in embodiments includes a calculating module, a generator, and a changing module. The calculating module calculates feature quantity concerning a flow of a contrast material for each pixel in a predetermined section based on temporal transition in signal intensity of the contrast material in a predetermined section of a plurality of X-ray images radiographed with time by using the contrast material. The generator generates a first color image in which color information corresponding to the feature quantity concerning the flow of the contrast material in a first section as the predetermined section is reflected in each pixel. The changing module changes the predetermined section to a second section that is within the first section. the generator generates a second color image in which color information corresponding to the feature quantity concerning the flow of the contrast material in the second section is reflected in each pixel based on the color information corresponding to the second section out of the color information corresponding to the feature quantity concerning the flow of the contrast material in the first section and the feature quantity calculated in the second section.
