PROBLEM TO BE SOLVED : To provide an Internet auction system capable of handling large amount property such as real estate.SOLUTION : In the auction system, which is provided with a home page 2 operated by an auction execution company 3, a register means for registering the property of a seller 5 on this home page 2, a credit company 4 in cooperation with the auction execution company 3 and a bidding means for a bidder 6 as a member of this credit company 4 to bid, and a bidder, who applies the highest price within an auction period, can make a successful bid, when the bidder 6 is to take part in auction by retrieving the property on the home page 2, the credit company 4 examines the qualification of the bidder 6 and when it is discriminated that the bidder satisfies the bidding qualification, a bid guarantee for taking part in auction is paid to the auction execution company 3 in place of the bidder 6.