To prevent an increase of cost of a whole system and a deterioration of a processing speed by limiting a commodity code added to one commodity to be one kind and also limiting commodity master data to be one per one commodity.

Before sales-registering of a commodity which is purchased by a customer, a transaction kind with the customer is judged. A file processor FP 2 retrieves a commodity local file LF to discriminates the presence/absence of the setting of commodity data including commodity data including a commodity code constituting an inquiry code and a unit price identification code. When commodity data is set, FP 2 outputs a response to the POS terminals 4a to 4c and when commodity data is not set, inquires of a storing processor 1 commodity data. Then a commodity master file MF is retrieved to acquire commodity master data including an inquiry code. POS terminals 4a to 4c, receiving commodity data from FP 2, sales-register-processes sales data of sales commodity based on this data.