A device for reconstructing a panoramic image of a dental arch using image data of a computed tomography, CT, image from a CT radiography device, comprising: a geometry correction unit configured to correct a geometry of the image data so that the CT image is correctly positioned in a three-dimensional space; a dental arch trajectory detection unit configured to detect a dental arch trajectory in the CT image; an active section setting unit configured to set an active image data section in the CT image; and a reconstructing unit configured to generate a panoramic image by summating image data of the image data active section of the CT image corrected in the geometry correction unit, characterized in that: the dental arch trajectory detection unit includes a position data setting part configured to set a standard dental arch and a rotate center point,RCP, coordinate, and a dental arch trajectory generator configured to generate a dental arch trajectory by using the standard dental arch set in the position data setting part, wherein the RCP coordinate is calculated by using the detected dental arch trajectory and device radiograph sequence information, the active section setting unit is further configured to calculate an X-ray irradiation path of a panorama image radiograph sequence for each voxel position of the dental arch trajectory by setting a positional coordinate of an X-ray source for each voxel position of the dental arch trajectory within the active image data section based on the detected dental arch trajectory and the RCP coordinate, and the reconstruction unit is further configured to generate the panoramic image by performing a summation of the X-ray irradiation path generated from each positional coordinate and image data of intersection areas between dental arch trajectory and the X-ray irradiation path, and arranging the summation result according to the dental arch trajectory. a geometry correction unit configured to correct a geometry of the image data so that the CT image is correctly positioned in a three-dimensional space; a dental arch trajectory detection unit configured to detect a dental arch trajectory in the CT image; an active section setting unit configured to set an active image data section in the CT image; and a reconstructing unit configured to generate a panoramic image by summating image data of the image data active section of the CT image corrected in the geometry correction unit, characterized in that: the dental arch trajectory detection unit includes a position data setting part configured to set a standard dental arch and a rotate center point,RCP, coordinate, and a dental arch trajectory generator configured to generate a dental arch trajectory by using the standard dental arch set in the position data setting part, wherein the RCP coordinate is calculated by using the detected dental arch trajectory and device radiograph sequence information, the active section setting unit is further configured to calculate an X-ray irradiation path of a panorama image radiograph sequence for each voxel position of the dental arch trajectory by setting a positional coordinate of an X-ray source for each voxel position of the dental arch trajectory within the active image data section based on the detected dental arch trajectory and the RCP coordinate, and the reconstruction unit is further configured to generate the panoramic image by performing a summation of the X-ray irradiation path generated from each positional coordinate and image data of intersection areas between dental arch trajectory and the X-ray irradiation path, and arranging the summation result according to the dental arch trajectory.