In an X-ray CT device according to an embodiment, reconstruction circuitry reconstructs a positioning image from projection data collected based on a detection signal of transmitted X-rays in positioning imaging performed at a first tube current. Circuitry detects body parts of a subject included in the positioning image. Storage stores information pieces relating to body parts, image quality levels for each of the information pieces relating to the body parts, and an X-ray count value corresponding to each of the image quality levels in an associated manner. The circuitry selects an image quality level corresponding to a desired body part. The circuitry acquires a second tube current based on the first tube current, an X-ray count value in the positioning imaging, and an X-ray count value associated with the selected image quality level. The circuitry controls an X-ray tube to perform main imaging based on the second tube current.
