According to the present document, a video decoding method performed by a video decoding apparatus may comprise the steps of: parsing a first flag and a second flag from a bitstream, wherein the first flag is related to whether weighted prediction is applied to slices referring to a picture parameter set, and the second flag is related to whether information relating to the weighted prediction exists in a picture header; parsing a prediction weighted table syntax from the picture header based on the first flag and the second flag; generating prediction samples for a current block in a current picture based on syntax elements within the prediction weighted table syntax; generating residual samples based on residual information; and generating reconstructed samples based on the prediction samples and the residual samples, wherein the second flag is parsed from the picture parameter set based on the first flag.