When slide show image data sets are generated from a plurality of image data sets, the image data sets, DVD-Video files representing the slide shows generated from the image data sets, and information representing reproduction order are stored in a manner that allows a user to access them so that pleasure of the slide shows for the user is not ruined. The user changes the images to be included in the DVD-Video files and the reproduction order, while referring to the image data sets, the DVD-Video files, and the information. A digitalization center newly generates DVD-Video files according to the changed images and the changed reproduction order.