PURPOSE: To develop a device which prevents repurchased coupons from unfairly being used to a wholesaler and also gives much information to customers.

CONSTITUTION: A store lends a customer an electronic communication device 14 and the customer knows a repurchase coupon 30 and its object goods via a display screen 16 of the device 14. The device 14 has a selection button 24 and a memory, the button 24 clearly shows the selection of coupons which the customer wants to repurchase and the memory records the selection before the customer comes to a purchase price adjustment office 43 and subtracts the sum which is equivalent to the coupons 30 from a purchase price.