A rearrangement volue operator 3 calculates a sum S of an error correction data Ea from a comparator 7 and a sum Sm of the image signal levels of four picture elements R00, R01, R10 and R11 from the rearrangement memory 2, and obtaining N and A from following equation S=C???N+A, where C is a predetermined image signal level, N is an integer falling in a range O???N???M, and A is an image signal le