PURPOSE: To display a magnified picture in a way that a contour of display of a graph or a character or the like is not made unclear with respect to a signal synthesizing a video signal of a natural picture and a display signal of a graph or the like from a personal computer or the like.

CONSTITUTION: Video signal inputs A, B are synthesized and the result is written in a field memory 2, scanning lines read sequentially are subject to interpolation processing in a line memory 7 which provides an output, the output is branched and one output is inputted to a selector 16, and the other is inputted to an interpolation processing circuit 17, in which different interpolation processing from that in the line memory 7 is executed and the result is inputted to a selector 16, a control section 6 counts number of synchronizing signals in the video signal input A to provide a signal output at a predetermined position, it is inputted to the field memory 2, the video signal input B is written in the field memory 2 at a predetermined position of the video signal input A and synthesized, a switching signal is inputted to the selector 16 and interpolation processing is selected for the video signal inputs A, B to provide an output.