A message, including ordering data regarding a price of a product that a purchaser wants to purchase and personal information including a credit card number of the purchaser, is given to a settlement agency computer from a purchaser computer used by the purchaser. The settlement agency computer determines whether to pay for the product for the purchaser, based on the ordering data and the personal information. In a case where it is determined to pay for the product for the purchaser, the settlement agency computer sends settlement permission information representing that payment can be made for the purchaser, to a seller computer used by a seller, while keeping the credit card number to be confidential. Hence, before delivering the product to the purchaser, the settlement is completed, and the credit card number of the purchaser is kept secret from the seller.