X-ray diagnostic device

An X-ray tube generates X-rays. A detector detects X-rays generated by the X-ray tube and transmitted through a subject. A C-arm is equipped with the X-ray tube and the detector. An arm support mechanism rotatably supports the C-arm. A top is on which the subject is placed. A bed supports the top so as to change a relative positional relationship along a horizontal direction between the C-arm andthe top. The bed supports the top so as to change a relative positional relationship along a vertical direction between the C-arm and the top. A mechanism control unit controls the arm support mechanism and the bed so as to a perpendicular extending from a focus of the X-ray tube intersects the top at a predetermined position thereon, and a distance interval between the X-ray tube and the predetermined position is fixed during rotation of the C-arm.