A data transfer system capable of lightening the load on a server and reducing the amount of data carried over a network. A search/registration unit of the server determines whether or not shape data in graphics information created by a three-dimensional application is registered in shape cache information and, if not registered, registers the shape data. If the shape data is registered, a data transfer unit replaces the shape data with designation information specifying the corresponding data in the shape cache information to generate graphics differential information, and transmits the generated information to a client. A registration unit of the client registers new shape data in shape cache information in accordance with the graphics differential information. A data restoration unit searches the shape cache information based on the designation information to extract the corresponding shape data, and replaces the designation information with the shape data to restore the graphics information.