PURPOSE: To provide high-vision display pictures with less line flickers by magnifying the pictures of a personal computer to threefold vertically and horizontally and performing an arithmetic processing among scanning lines.

CONSTITUTION: This converter is composed of an AD conversion part 1 for converting R video signals to digital data and performing serial-parallel conversion further, field memory 2 for successively storing the digital data (R data) of the inputted R video signals, line memory 3 for storing the R video signals for one scanning line, an averaging processing part 4 for inputting data read from the frame memory 2 and the corresponding data read from the line memory 3 while making a timing in a horizontal direction synchronized and performing an averaging processing, a switching part 5 for selecting one of the data read from the frame memory 2 and the output data of an arithmetic processing part 4, a multiplexer 6 for selecting and outputting one scanning line data from inputted three scanning line data and a DA conversion part 7 for parallel-serial converting the R data and converting them to analog R signals further.