A cash processing system capable of diversified cash processes by means of a cash processor, and reducing calculator resources to achieve cost reduction. The cash processing system has a cash processor and a server connected to the cash processor through a network. The server provides an extension function program according to a download request from the cash processor. The cash processor includes: a first storage unit which stores a basic function program; a second storage unit which stores an extension function program; and a control unit which executes the basic function program and the extension function program. The control unit stores, according to the reception of a processing request which instructs the execution of the cash process, downloads, from the server, an extension function program that corresponds to the cash process included in the processing request, and stores the extension function program in the second storage unit.