PURPOSE: To reduce the capacity of a memory which converts the image data into the data on each block.

CONSTITUTION: A block line memory 11 inputs the image data of non-interlace. These data are read out every (8×8) picture elements and then compressed and coded through a DCT part 12, a quantizing part 13, a zigzag scanning part 14, and a coding part 15. Then the processed data are supplied to a recording medium like a memory card, etc., through a terminal 16. Meanwhile the coding value of each block is calculated by a block coding value calculation part 18 and supplied to a coding value control part 19. The part 19 compares the actual coding value of the part 15 with the coding value assigned to each block in order to control the coding value.