To provide an option article selling method of domestic electric appliances capable of suppressing the cost of the option article, miniaturizing it, and optimally controlling it.

A marker opens a web site on the Internet with a Web server 1, and, when a user having purchased the appliance orders an option article on the web site, delivers the option article to the users home from a cooperated store. When the option article is mounted on the appliance, the control contents of the appliance must be changed, so that the Web server 1 transmits the appliance purchased by the user and control software suitable for the option article. Therefore, the appliance can be controlled by the transmitted control software after that, so that the appliance can operate optimally.