To perform safer mail-order selling by avoiding money trouble involved in a sale contract performed through a network.

This mail-order system makes a merchandise sales contract by utilizing a network constructed by mutually connecting a plurality of terminal devices through communication lines, there are a purchaser 1 accessing the network through a terminal device used by the purchaser oneself and a seller 2 presenting a home page, a site, etc., to the network and sells merchandise, and a mail-order support server 3 being the third party organization with respect to the purchaser 1 and the seller 2 is provided for this system. The server 3 is provided with a mail transmitting and receiving part 31 transmitting and receiving notification to/from the outside through the network, a price receiving part 32 receiving a price transmitted from the outside, a money transmitting part 33 transmitting a price to the outside and a managing part 34 which manages each of the parts 31 to 33 and also monitors transaction situation between the purchaser 1 and the seller 2.