1. A method for calculating 3D volume of cerebral hemorrhage lesion, comprising the steps of: setting ROI of normal cerebral parenchymal region and ROI of cerebral hemorrhage lesion, respectively, based on a plurality of images of continuous slices obtained by imaging a head affected by a cerebral hemorrhage by an X-ray CT device; determining mean value of CT values of pixels within said ROI of normal cerebral parenchymal region for a plurality of images; determining, based on the reference with the mean value of one image, the amount of shift of the mean value of any other images; using the shift value for each image to adjust the CT value of pixels within the ROI of the cerebral hemorrhage lesion for each image; specifying the maximum value of CT values after adjustment through a plurality of images; and calculating 3D volume of cerebral hemorrhage lesion given by the following equation: 3 ⁢ DVolume = ∑ n = 1 N ⁢ Index n * f ⁡ ( DEOV , SFOV , SliceThickness , Magnification , Λ ) ⁢ ⁢ if ⁢ ⁢ Mean 1 < P n ≤ Maximum , Index n = P n - Mean 1 Maximum - Mean 1 ⁢ ⁢ if ⁢ ⁢ P n ≤ Mean 1 , Index n = 0 [ equation ⁢ ⁢ 1 ] where: n: pixel number of pixel within the ROI of cerebral hemorrhage lesion in a plurality of images; N: total number of pixels within the ROI of cerebral hemorrhage lesion in a plurality of images; p n : CT value after adjustment within the ROI of cerebral hemorrhage lesion; DFOV: dimension of defined FOV; SFOV: dimension of scanned FOV; SliceThickness: thickness of a slice; and Magnification: magnification value.