An image compressing apparatus divides an image into plural tiles, decomposes each tile into plural sub band by frequency conversion, and conducts bit plane encoding of each sub band for each encoding unit, wherein the image compressing apparatus includes a code discarding unit selectively discarding a code obtained by the bit plane encoding for each encoding unit, and wherein the code discarding unit includes a discard amount setting unit that makes generally even the amount of code discarding in the encoding units that are in mutually adjacent relationship across a tile boundary.