Disclosed are a rich media sever, a rich media transmission system, and a rich media transmission method, which are adaptive to network environments. The rich media server includes an interfacing unit for communicating with a terminal, which requests rich media; a media processing unit for processing at least one piece of media corresponding to the request; a rich-media encoding unit for encoding at least one piece of media, which is output from the media processing unit, to produce rich media, and outputting the rich media to the interfacing unit in order to provide the rich media to the terminal; and a controller for determining importance rates of pieces of media constituting the rich media, based on reproduction information of the rich media, and controlling at least one of the media processing unit and the rich-media encoding unit to convert a transmission processing for the at least one piece of media based on the determined importance rates.