To surely process the daily maintenance equivalent to the single commodity reference file of a file processor even against occurrence of a fault in a store processor.

A store processor 1 detects the change reservation data which define the date set after a prescribed number of secured days from a system date as a change execution day out of a change reservation file 7 after the change reservation processing is started. Then the processor 1 sends the change reservation data to a file processor 3. The processor 3 stores the change reservation data received from the processor 1 in a unit price change file 9. When the change reservation data including the change execution day that is coincident with the system date is detected, the unit price data corresponding to the relevant unit commodity code of a unit commodity reference file 8 are rewritten based on the detected change reservation data.