PURPOSE: To confirm commodities of good sale by storing the cumulative number of all sold commodities and that of sold commodities of each classification and calculating and displaying a ratio of the latter to the former.

CONSTITUTION: The number of sold commodities is cumulatively stored in not only the storage area for the cumulative number of sold commodities of the classification but also the storage area for the total cumulative number of all sold commodities by the signal from a storage control part 17. The total cumulative number of all sold commodities and the cumulative number of sold commodities of the selected classification are read from a RAM memory by an arithmetic part 18, and a ratio of the latter to the former is calculated, and the calculated result is displayed with light emitting diodes in a sale ratio display window 4 by a display control part 16. Thus, commodities of good sale are confirmed.