A video decoding method performed by a video decoding apparatus, according to the present document, may comprise the steps of: parsing, from a bitstream, number information about the number of slices having heights specifically signaled within a tile of a current picture; on the basis of the number information, parsing, from the bitstream, height information about the heights of the slices having the specifically signaled heights; deriving the number of slices within the tile on the basis of the number information and the height information; generating prediction samples by performing at least one of intra prediction and inter prediction on a current block of the current picture on the basis of the slices within the tile; and generating reconstructed samples on the basis of the prediction samples.