An image decoding method according to the present invention comprises the steps of: deriving most probable mode (MPM) candidates on the basis of an intra-prediction mode of candidate blocks; determining whether the MPM candidate having the intra-prediction mode, which is the same as that of a current block, exists among MPM candidates; and deriving the intra-prediction mode of the current block on the basis of the determination, wherein the candidate block includes a neighboring block which is adjacent to the current block, and a non-neighboring block which is not adjacent to the current block.