An X-ray diagnostic apparatus according to embodiments includes an X-ray tube assembly and a grid potential control circuitry. The X-ray tube assembly includes a filament that emits electrons, a target that generates X-rays by receiving the electrons, and a grid having a potential for adjusting a potential gradient around the filament. The grid potential control circuitry switches the potential of the grid to a potential where the potential gradient around the filament becomes greater than a potential gradient generated by a potential of the filament and a potential of the target.