This invention relates to a conversion control method of an external device input mode. In the image devices of DVD of VCR connected with TV sets, when a remote controller receivers input signals of specific keys set on the remote controller for watching the signals played and output by DVD or VCR, it leads them into the system and generates control signals for automatically converting the input mode of the external connecting device and sends them to the external connection device to output the play signals. Even though a user does not select the external input mode of TV, the user watch signals output and played by DVD via TV pictures.