To protect purchaser's privacy in electronic commodity sale utilizing a network.

A commodity sale method is performed among a purchaser 20, a seller 30, and an mediator 40 by utilizing the network. The purchaser 20 selects commodity discrimination information on a seller's home page picture and sends a password to the seller 30 together with the selected commodity discrimination information. The seller 30 generates commodity discrimination information readable by only the anonymous purchaser based on the commodity discrimination information and sends the generated commodity discrimination information to the purchaser 20. The purchaser 20 sends the commodity discrimination information to the mediator 40 together with discrimination information which can be specified by the purchaser, and the mediator 40 sends the commodity discrimination information to the seller 30. The seller 30 obtains a commodity based on the commodity discrimination information and sends it to the mediator 40, and the mediator 40 sends the commodity to the purchaser 20.