A contents additional services inquiry server for receiving inquiries for additional services provided by a contents center and a third-party contents additional services providing server, wherein a registration request specifies a contents identifier uniquely identifying contents, and requests registration of registration request information including each additional service information regarding service that can be provided with respect to the contents having the contents identifier and provider location information regarding a location of a respective provider of each additional service. Registration request information registered by the contents center and registration request information registered by the third-party contents additional service providing server are separately stored. The registration request information specified by the contents identifier is searched and returned when there is a request for the additional service, where registration request information registered by the contents center and registration request information registered by the third-party contents additional service providing server are separately presented.