PURPOSE: To suppress propagation of an error with simple circuit constitution and without sacrificing picture quality and cost altogether by sending the result of comparison between a maximum difference and a preset threshold value for using as an index for each block.

CONSTITUTION: A delay device 6 and a subtractor 7 calculate a difference with an adjacent face element as to picture elements in a TV pattern, and a block processing device 8 collects plural picture elements to constitute a block. A maximum value detector 9 obtains a maximum value in the difference in all picture elements included in the block, a comparator 10 compares the maximum value with the preset threshold value for the quantity and the result is added to a transmission data by an index adder 12 as 1-bit information. If an error takes place on the way of transmission, and when the error propagation reaches a block smaller than the threshold value with a difference from the adjacent picture element, since the difference with the adjacent picture element exceeds the threshold value, the picture element discriminates it as an error and it is replaced into the adjacent picture element. Thus, the propagation of error is suppressed without sacrificing both the picture quality and the transmission cost with simple circuit constitution.