An image decoding method performed by a decoding apparatus, according to the present document, comprises the steps of: acquiring image information comprising a flag indicating whether or not one chroma quantization parameter table is to be applied with respect to chroma components, and prediction information and residual information regarding the chroma components; on the basis of the flag, deriving a chroma quantization parameter for the chroma components; deriving residual samples for the chroma components on the basis of the residual information and the chroma quantization parameter; and generating a reconstructed picture on the basis of prediction samples, which have been derived on the basis of the prediction information, and the residual samples.