Advertising information input control module of a POS system receives advertising information, and a billing amount calculating module calculates a billing amount based on advertising information received by input control module. A payment confirming module confirms payment of the billing amount calculated by the billing amount calculating module, and an advertising information storing control module stores the advertising information in a storing device. A check-out information input control module receives input of customer check-out information, and an advertising information retrieving module retrieves the advertising information stored in the storing device. A printing data generating module synthesizes or combines check-out information with the advertising information so as to generate printing data, which is output at a printing device, and printed as a receipt with an ad.