PURPOSE: To provide a POS system which is rich in readiness and capable of instantly coping with even the change of a stamp mark and printing the stamp mark for which a prescribed change has been performed on a slip.

CONSTITUTION: This system is provided with a display part 3 displaying stamp mark data, a stamp mark data storage part 4 storing plural kinds of stamp mark data, a stamp mark data preparation processing part 2 supplying inputted stamp mark data to the display part 3 and supplying the stamp mark data displayed on the display part 3 and an inputted registering number to the stamp mark data storage part 4 and a stamp mark data printing processing part 5 reading corresponded stamp mark data from the stamp mark data storage part 4 by the inputted registering number, supplying it to a printing part 6 and printing it on a slip.