To provide a commerce method capable of efficiently carrying out a business negotiation between a purchaser and a seller of a commodity via a network.

A purchase receiving means 32 receives a person desiring to purchase a commodity via a purchase accepting web page 40 released on the Internet 2. A purchase mediating means 33 selects a seller conforming to purchase condition data sent from a terminal device 3 of the purchaser received by the purchase receiving means 32, and it sends the purchase condition data to a terminal device 4 of the selected seller. When sales condition data responding to the purchase condition data sent from the terminal device 4 of the seller is received, the purchase mediating means 33 sends list data of the purchase condition data and purchase condition correction confirmation data to the terminal device 3 of the purchaser, and when corrected purchase condition data is received from the terminal device 3 of the purchaser, the corrected purchase condition data is sent to the terminal device 4 of the seller.