Original images, large images, medium images and thumbnail images are registered with a server system. An original-image file is transmitted from a client computer to the server system. The server system converts the format of the original-image file to generate a large-image file, generates a medium-image file, in which the quantity of data is less than that of the large-image file, from the large-image file, and generates a thumbnail-image file, in which the quantity of data is less than that of the medium-image file, from the medium-image file. The original-image file, large-image file, medium-image file and thumbnail-image file are placed on one folder and stored in an image file unit. After the folder containing the original-image file, etc., has been stored in the image file unit, the user of a client computer having access privileges is capable of accessing files such as the large-image file.