The present embodiment, for an intra prediction method used by an intra prediction device, provides the method comprising: decoding, from a bitstream, mode information indicating use of a prediction derivation mode for a prediction mode block; deriving an intra prediction mode of each pixel group from intra prediction modes of pre-reconstructed reference pixels at a plurality of positions near the prediction mode block for each pixel group including one or more pixels in the prediction mode block; and intra-predicting the pixels in each pixel group using the intra prediction mode of each pixel group.