To provide a transaction conclusion determining method assuring the maximization of profit when a loss incurred in a transaction by limiting the loss to be within a range predetermined by the auctioneer with each bidder bidding a rightly assessed value.

In the transaction of a commodity by two-way electronic bidding, the auctioneer determines, concerning the commodity, the maximum amount of permissible loss and, dependent on the number of transactions, the minimum price column for the buyer or the buying price (the minimum limit below which no selling occurs) and the maximum price column or the selling price (the maximum price beyond which no buying occurs). The auctioneer controls the number of transactions and the transaction assessment value (the bid price) by using these three threshold assessment values (prices).