A radio line is easily influenced in its nature by attenuation or reflection of an electromagnetic wave or the like and the surrounding environment. Due to this fact, a variation of the data transfer speed frequently occurs at the time of image streaming so as to become a hindrance to reproduction of an image at the receiving terminal. A distribution server is provided with a multiplexer for multiplexing information indicating the transmission start time for the image data and a switching unit for switching an image bit rate in response to a request from the receiving terminal. The receiving terminal uses information indicating a transmission start time for the image data, monitors the receiving bit rate and sends out a request for transmission of the most-suitable image bit rate in response to a comparison thereof.