PURPOSE: To display a master screen of the NTSC signal and a slave screen of the HD signal after the synthesization of both screens and furthermore to attain the function of an HDTV/NTSC converter with addition of a simple circuit.

CONSTITUTION: When a switching circuit 64 is set at the side of a 1st D/A converter 54, the NTSC signal is converted into a digital signal and then into an analog signal after the time base conversion. Meanwhile the HD signal is converted into a digital signal and then into an analog signal after undergoing the processing for a prescribed slave screen size and the time base conversion. Such NTSC and HD signals are synthesized by a synthesizing circuit 66. Then a slave screen of the HD signal is displayed on a part of a master screen of the NTSC signal by a high-vision monitor 38. When the circuit 64 is switched to the side of a synchronizing separator 62, the circuit 66 synthesizes the synchronizing signal of the NTSC signal to the HD signal processed for a prescribed size. Then a high-vision broadcast screen is displayed by a general-purpose NTSC receiver.