To obtain electronic transaction characterized by that a price is determined by allowing respective companies to bid, on the basis of a minimum purchase amount that a consumer of the Internet presents.

A consumer 1 registers 4 individual information and a password in a file 3 presented by access to a homepage of an electronic transaction running company 2. The consumer accesses the homepage of the electronic transaction running company for password verification 6, when necessary and inputs a necessary item 9 to the presented file 8 on condition that the consumer is authenticated 7. The electronic transaction running company e-mails inputted necessary items to respective companies 10, which present bid amounts 11 to the electronic commerce running company. The presented information of the respective companies is e-mailed to the consumer and examined, and the consumer specifies an amount and its company to enter a contract.