Medical image data is utilized, physical values are assigned to body parts based on image information, and the target organs are separated from the image data to prepare a 3D biodata model to thereby realize a data model unique to a patient, having an internal structure, and enabling dynamic simulation of a live body. The same target part of a body is captured by CT and MRI to obtain medical images. Sets of pairs of CT images and MRI images are set, a plurality of features showing the same locations are selected and set from the sets of CT images and MRI images, a conversion coefficient between the CT images and MRI images is obtained, and this conversion coefficient is used to rearrange the MRI images by projection transforms and linear interpolation, combine them with the contours of the CT images, and correct their positions in the contours. Further, the images are used to prepare a 3D data model.