Device ID detecting means detects an ID of a device on another party. Next, it is checked whether the device ID is included in historical information stored in authentication histories storing means. If the device ID is included in the historical information, authenticating means performs authentication with authenticating means on another party. Thereafter, when an AV data transmission direction is provided from a user to command input means, the command is notified through command control means to AV data transmitting means which starts transmission of AV data.