To provide an electronic commercial transuction system and a goods selling method capable of properly determining the price and effectively utilizing the resource in the electronic commercial transuction having a function of auction.

A condition that the security money should be paid by electronic money is given to both of an exhibitor and a bidder in the auction. The security money from the exhibitor is returned to the exhibitor when the trading is normally completed, and is used for compensating for the loss received by a successful bidder when some trouble caused by the exhibitor occurs. On the other hand, the security money from the successful bidder is used for the payment in trading when the trading is normally completed, and is used for compensating for the loss received by the exhibitor when some trouble caused by the successful bidder occurs. This system can forbid the irresponsible exhibition and bid, and prevent the fraud, and further the benefit by practical use can be expected by practically using the temporarily paid security money.