PURPOSE: To process all blocks by the same one line by devising to process a residual line to be produced when the line in one frame is blocked by the number of averaged lines.

CONSTITUTION: A coding part is composed of a forecasting coding circuit 1 and a multiple circuit 2 and a decoding part is composed of a separating circuit 3 and a forecasting decoding circuit 4. To process a residual line, one block is five lines, and a picture is thinned out in the coding circuit 11 for the block of five lines. Next, an effective picture number is shifted during four line time and all blocks process four line time unit in the latter part multiple circuit 2. On the other hand, even in the decoding part, the same processing is executed. As this result, all blocks are processed by the same line number. A line number per block is n=4 and even concerning a free n, the same can be obtained.