To provide an on-line auction system capable of coping with various dealing conditions such as payment to bank, credit card and debit card, besides cash transactions, and enlarging the dealing to equally provide the benefit to both of a seller and a buyer while keeping the balance between demand and supply.

The seller registers an exhibit or makes a bid for the exhibit from a terminal 3 to a WEB server 2 of a mediator connected to the Internet network 1, and the buyer registers desired goods or makes a bid for purchase. With respect to a successful bid for goods, the selective successful bid opportunities are given under the consideration of the dealing conditions and a condition of goods, besides the price, which increases the possibility of the successful bid for the goods to the seller, allows the buyer to easily get the desired goods, and totally activates the auction system.