An image file editing method includes an analysis step of analyzing a compression format of each of a plurality of images included in a plurality of image files, a display step of displaying analysis results together with thumbnail images each of which corresponds to one of the plurality of images, a selection step of selecting images based on the thumbnail images, a determination step of determining, based on the results obtained in the analysis step, whether or not a compression format of each selected image is changeable, a compression step of applying a changed compression format, and an output step of collectively outputting selected images as a single image file.