A simple, easy, and safe electronic settlement system is provided. A user terminal such as a cellular phone is wirelessly connected to a synchronizing server. A cashier server of a mail order retailer activates a virtual cashier terminal, and connects to the synchronizing server. The synchronizing server sets a transaction identifying number in order to identify the transaction, and sends to the user terminal information about the cashier server and the transaction identifying number. A user confirms the cashier server, and returns the transaction identifying number to the synchronizing server. The synchronizing server completes a transaction between the virtual cashier terminal and the user terminal, both of which are corresponded to each other by the transaction identification number. The user can complete a settlement of mail order without telling his or her personal information such as a credit card number or a password to a mail order retailer. A security of the system is improved.