A video decoding method performed by a video decoding device according to the present document may comprise the steps of: acquiring image information from a bitstream, wherein the image information includes a picture header associated with a current picture, and the current picture includes multiple slices; based on the picture header, acquiring at least one of a first flag indicating whether information required for an inter-prediction operation exists in the picture header and a second flag indicating whether information required for an intra-prediction operation exists in the picture header; based on at least one of the first flag and the second flag, generating prediction samples.