In the case where a three-dimensional position of a moving body is calculated based on image data taken by a plurality of cameras that are synchronized, high performance equipment and system such as a system to make the synchronization among the plurality of cameras and a camera having a built-in function to make the synchronization are required. It is also required to fix the camera position with high accuracy beforehand. It is made possible to calculate a trajectory of a moving body as a target in the three-dimensional space using image data taken by a plurality of cameras that are non-synchronized mutually, thereby solving the above issue. And positions of respective cameras are calculated in the three-dimensional space from a plurality of reference points having fixed position coordinates in the three-dimensional space that are commonly shown in the image data of the respective cameras, thereby solving the above issue.