An X-ray diagnostic apparatus according to an embodiment includes: an X-ray tube including a target configured to generate X-rays in response to emission of electrons thereto, a plurality of filaments configured to emit electrons into substantially the same position on the target, and a grid used in common among the plurality of filaments; intermediate potential setting circuitry configured to set intermediate potential in a position between the plurality of filaments and the target by using the grid; and filament potential controlling circuitry configured to change one or more filaments selected from among the plurality of filaments to emit the electrons to the target, by controlling potential levels of the plurality of filaments with respect to the intermediate potential for each filament, in conjunction with switching of X-ray tube voltage.