In a case in which the size of a moving body changes by a position of the moving body, in order to accurately track the moving body without an effort of the user regardless of a change in the size, the present disclosure estimates a size of the moving body in each of the images of the frames, updates template data based on the estimated size of the moving body, and compares a candidate region that is a candidate of a region where the moving body is present in each of the images of the frames with the template data, and determines whether or not the moving body is positioned in the candidate region based on the comparison result.