An apparatus obtains first transformation information, such as a first transformation matrix, to be used for coordinate transformation between a coordinate system in an overall image prepared beforehand and a coordinate system in a first captured image, by comparing a feature point extracted from the overall image and a feature point extracted from the first captured image. In a case where the first transformation information is updated, the apparatus generates a partial image from the overall image based on an image-taking position of a just preceding image, and compares a feature point extracted from the partial image with a feature point extracted from a captured image to be used for updating of the first transformation information, and accordingly obtains transformation information for updating. The apparatus updates the first transformation information by using the obtained transformation information for updating. Thus, accuracy of tracking processing is improved.