An X-ray diagnostic apparatus of an embodiment includes processing circuitry. The processing circuitry determines a concentration of a contrast agent in contrast-enhanced image collection based on first reference information in which a recommended contrast in a contrast-enhanced image is associated with each region of interest to be subject to collection of the contrast-enhanced image, and on second reference information that indicates a relation among a generation condition of an X-ray, a concentration of a contrast agent, and a contrast. The processing circuitry calculates setting information of an injector to inject a contrast agent to the subject based on the determined concentration of a contrast agent.