An effective electronic settlement system in which the number of checks is small. The electronic settlement system includes a data storage device such as an IC card in which value information is stored, a client device provided with an information input/output function to the data storage device, a store device for providing commodities or services, a settlement management device for managing settlement between the data storage device and the store device, and a communication system for connecting the client device, the store device, and the settlement management device so as to enable bidirectional communication. The settlement management device creates, based on settlement request information from the store device, settlement information for making settlement by the data storage device, subjects the settlement information to an encryption processing by using a common key shared by the settlement management device and the data storage device, and transmits the settlement information subjected to the encryption processing to the client device, and the client device outputs the settlement information received from the settlement management device to the data storage device.