The present invention generates coupon distribution key data in a key generation section (23) when distributing a coupon on advertising data; writes the coupon distribution key data to an IC card (50); manages memory identification data and the coupon distribution key data while associating them each other in a coupon management device (20); transmits the memory identification data and the coupon distribution key data stored in the IC card (50) from a user terminal device (30) to the coupon management device (20) when the user terminal device (30) has been operated to purchase a commodity; transmits coupon possession data to an electronic commerce site (40) if they coincide with the memory identification data and the coupon distribution key data managed in the coupon management device (20); makes a payment while allowing the coupon reflected therein. This allows the electronic commerce site, which published an advertisement, to authenticate that a user has obtained the coupon properly, which has been distributed to the user via an electronic advertisement that exists in an outdoor space or the like.