PURPOSE: To predict the code quantity with high accuracy and to prevent the deterioration of a reproduction image.

CONSTITUTION: A Huffman coding part 16 Huffman-codes the output of a data rounding part 4 with a code quantity based on a distribution value classified by a block from a block classification code distribution value computing element 9. The output of the data rounding part 4 is converted to an absolute value by an absolute value converting part 5 and given through a selector 22 to accumulation adders 6 and 7. A zero detecting part 21 detects whether or not the output of the absolute value converting part 5 is '0' and at the time of '0' a coefficient α is selected by the selector 22. Thus, the code distribution value classified by the block from the block classification code distribution value computing element becomes a large value when coefficients '0' are many, and is approximately coincident to the code quantity at the Huffman coding part 16. Thus, all outputs of the data rounding part 4 are coded and the deterioration of the reproduction image is prevented.