An X-ray CT device according to an embodiment includes a gantry, a top board, and a movement mechanism. The gantry includes an X-ray tube that generates X-rays and a detector that detects the X-rays. The top board inserts the subject into the opening section of the gantry. The movement mechanism moves the top board in a longitudinal direction. Furthermore, the position of the top board in a vertical direction at the position that intersects with the path of the X-rays is changed at substantially the same slope relative to the movement distance of the top board when the top board is moved in the longitudinal direction.
