Upon reception of a DDC access request from an external device connected to an HDMI port, a television receiver sets an electric potential of an HPD signal to ON level. Upon reception of an HDCP authentication initiation request from the external storage device after EDID is transmitted in response to a request from the external device, it is checked if an HDMI port to which that external device is connected is selected from a plurality of HDMI ports. If it is determined that the corresponding port is not selected, the control waits for selection of an HDMI port to which the external device is connected. If the corresponding port is selected, an electric potential of HPD signal is set at OFF level. After an elapse of 100 msec, the electric potential of the HPD signal is resumed to the ON level.