1. An X-ray diagnostic apparatus comprising: an X-ray imaging unit including an X-ray tube and an X-ray detecting unit to generate an X-ray image; an image generating unit generating a 3D non-blood vessel image and a 3D blood vessel image from an original 3D image generated by the X-ray diagnostic apparatus or an X-ray CT apparatus; a projection image generating unit generating a non-blood vessel projection image from the 3D non-blood vessel image and generating a blood vessel projection image from the 3D blood vessel image; a positional shift identifying unit identifying a positional shift between the X-ray image and the non-blood vessel projection image; a correcting unit correcting the blood vessel projection image on the basis of the positional shift; and a display unit displaying the X-ray image and the corrected blood vessel projection image.