To eliminate a troublesome money exchange between customers and to save the trouble to issue another slip by generating and subtracting payment- completion from payment-incompletion data and deleting it, and performing an account process with the same slip number.

A controller 3 generates a slip number corresponding to an order, generates order data on all ordered articles, and send payment- incompletion data before an account process to a POS main body 4. The POS main body 4 generates payment-completion data from the payment-incompletion data and sends them to the controller 3. Then the controller 3 deletes the payment-completion data from the payment-incompletion data, and generates and sends remaining payment-incompletion data altered with the same slip number to the POS main body 4, thereby performing the account process. Therefore, when one specific person in a group of persons occupying one table leaves the table, the payment of the person can easily be handled as to ordering accounting of the group.