To provide a character display processing unit that synthesizes character data of an optimum size for each display device with a video signal.

When a display system signal 40 of a display device 81 indicates correspondence of a high definition image or non-interlace scanning, a character size selection circuit 10a selects a character size displayed smaller and when the display system signal 40 of the display device 81 indicates correspondence of a standard image or interlace scanning, the character size selection circuit 10a selects a character size displayed larger. A character data expansion circuit 11a converts input character data 31 into a character video signal 32 of a selected character size. A video synthesis circuit 12 synthesizes the character video signal 32 with an input video signal 30 and outputs the synthesized signal. Thus, the display device 81 displays character data of the optimum size selected in response to the characteristic of the display device.