A picture coding method provides coding an input picture. The method includes dividing the input picture into a plurality of blocks, coding the input picture on a block basis to obtain coded data of each block, and decoding the coded data of each block on a block basis to obtain a reconstructed picture having a plurality of blocks. The method also includes removing coding distortion in an area disposed on both sides of a block boundary between a first block and an adjacent second block in the reconstructed picture having the plurality of blocks. Each block is adaptively decoded either as a field structure block, including only even field pixels or only odd field pixels, or a frame structure block, including odd field pixels and even field pixels. The method further includes storing the reconstructed picture, for which coding distortion is removed, as a reference picture.