An image encoding method includes: selecting, for each processing block, one of intra prediction modes specified by a coding standard, and performing intra prediction according to the intra prediction mode, wherein the intra prediction modes include a lower-left reference mode in which a processing block located at lower left of a current processing block is referred to, the processing blocks include a first processing block and a second processing block located at upper right of the first processing block, the second processing block being equal in size to the first processing block, the coding standard defines that information on the second processing block is written into a bitstream after information on the first processing block, and in the intra prediction, (i) selection of the lower-left reference mode is prohibited and intra prediction is performed on the second processing block, and, (ii) intra prediction is performed on the first processing block.