When an input signal is signal-converted and is output, the copyright of a signal to be signal-converted is reliably protected. In an additional information detection/determination section, digital watermark information, CGMS information, etc., which are superposed on or added to an input luminance signal, are detected, and it is determined whether or not a signal which is to be signal-converted in a signal conversion section should be output on the basis of the detected additional information. When additional information for prohibiting or limiting copying has been superposed on or added to the input luminance signal, a switching circuit for output control is turned off so that the signal which is signal-converted in the signal conversion section is not output to the outside.