An image decoding method performed by a decoding apparatus according to the present disclosure comprises the steps of: obtaining intra prediction information including at least one of MPM flag information, MRL index information, and planner flag information from a bitstream; checking the MPM flag information; checking the MRL index information on the basis of a case where the MPM flag information indicates that the MRL index information is checked; checking the planner flag information on the basis of a case where a value of the MRL index information is 0; deriving an intra prediction mode for a current block on the basis of the check for the planner flag information; deriving prediction samples for the current block on the basis of the intra prediction mode for the current block; and generating a reconstructed picture on the basis of the prediction samples.