This invention scans a block using a window having a size of p×q pixels, and encodes p×q sub-block data each formed from pixel data at relatively identical positions in windows. A blocking unit receives a 16×16-pixel block image. A sub-block division unit scans the received block for each 2×2-pixel window, and generates 2×2 sub-block data each having a size of 8×8 pixels. Each sub-block is formed from pixel data at relatively identical positions in windows. A variable length coding unit encodes each sub-block data. When the sum of encoded sub-block data exceeds an allowable encoded data amount, a sub-block elimination unit eliminates encoded sub-block data until the sum becomes equal to or smaller than the allowable encoded data amount. The sub-block elimination unit outputs the remaining encoded sub-block data as encoded data of a block of interest.