Abstract: Disclosed are on-line auction system and an on-line auction method, in which a seller can distribute purchase orders according to the production schedule and can sell the goods at higher prices, and a bidder can receive the goods he wants to purchase at a time he wants. In the auction system and the auction method, if an excessive demand is detected, a seller registers information of goods to be produced and a bidder registers demand information about goods the bidder wants to purchase. When there exists an excessive demand, conducted is an auction, including an order caused the excessive demand and orders still in a waiting state. Then, an order with the lowest bid price is excluded from the auction, while orders in the waiting state after a predetermined time has passed are converted to production-determined orders.