CT data processing devices and CT data processing methods

CT data processing apparatus (10), comprising: a center calculation part (14) which calculates a center of the body (41) of an examinee to tomography CT data; a start points-setting part (17) that identifies a spine position (45) on the tomographic CT data and an initial location (46) sets, wherein a first reference point (47) for initial determination on a muscle layer (37) opposite to the is arranged on that side of the spine position (45) with respect to the center of the body (41); a muscle layer determination part (18) which determines whether the muscle layer (37) in a first region (48) is present or not, which is set based on the first reference point (47), and when it is determined that the muscle layer ( 37) (in the first region 48) is present, a location on the muscle layer (37) in the first region (48) as the new first reference point (47) is adjusted, and thus determines whether the muscle layer (37) (in the first region 48) or not present, while the first reference point (47) (from the initial point 46) is moved; and a separation line calculating part (19), the calculated a dividing line, that the separating line separating a subcutaneous fat area by an inner fat area, by the first reference locations (47) extends.