A picture decoding method performed by a decoding apparatus, comprising: obtaining image information including information related to a quantization parameter, QP, from a bitstream, wherein the information related to the QP includes information related to a luma QP and information related to chroma QPs; deriving the luma QP based on the information related to the luma QP; deriving the chroma QPs based on the information related to the chroma QPs, wherein the chroma QPs include a first chroma QP for a Cb component and a second chroma QP for a Cr component; generating a reconstructed picture including reconstructed samples based on the luma QP, the first chroma QP for the Cb component and the second chroma QP for the Cr component, wherein deriving the luma QP based on the information related to the luma QP comprises: deriving a predicted luma QP based on previously coded quantization parameters, deriving a QP delta value based on information on an absolute value of the QP delta value and information on a sign of the QP delta value, wherein the information on the absolute value of the QP delta value and information on the sign of the QP delta value is included in the information related to the luma QP; and deriving the luma QP based on the predicted luma QP and the QP delta value, characterized in that deriving the chroma QPs comprises: deriving the first chroma QP for the Cb component based on the luma QP and a first chroma QP mapping table for the Cb component; and deriving the second chroma QP for the Cr component based on the luma QP and a second chroma QP mapping table for the Cr component, wherein both an input of the first chroma QP mapping table and an input of the second chroma mapping table are based on the luma QP, wherein the first chroma QP mapping table for the Cb component is a separate mapping table from the second chroma QP mapping table for the Cr component. obtaining image information including information related to a quantization parameter, QP, from a bitstream, wherein the information related to the QP includes information related to a luma QP and information related to chroma QPs; deriving the luma QP based on the information related to the luma QP; deriving the chroma QPs based on the information related to the chroma QPs, wherein the chroma QPs include a first chroma QP for a Cb component and a second chroma QP for a Cr component; generating a reconstructed picture including reconstructed samples based on the luma QP, the first chroma QP for the Cb component and the second chroma QP for the Cr component, wherein deriving the luma QP based on the information related to the luma QP comprises: deriving a predicted luma QP based on previously coded quantization parameters, deriving a QP delta value based on information on an absolute value of the QP delta value and information on a sign of the QP delta value, wherein the information on the absolute value of the QP delta value and information on the sign of the QP delta value is included in the information related to the luma QP; and deriving the luma QP based on the predicted luma QP and the QP delta value, characterized in that deriving the chroma QPs comprises: deriving the first chroma QP for the Cb component based on the luma QP and a first chroma QP mapping table for the Cb component; and deriving the second chroma QP for the Cr component based on the luma QP and a second chroma QP mapping table for the Cr component, wherein both an input of the first chroma QP mapping table and an input of the second chroma mapping table are based on the luma QP, wherein the first chroma QP mapping table for the Cb component is a separate mapping table from the second chroma QP mapping table for the Cr component. deriving the first chroma QP for the Cb component based on the luma QP and a first chroma QP mapping table for the Cb component; and deriving the second chroma QP for the Cr component based on the luma QP and a second chroma QP mapping table for the Cr component, wherein both an input of the first chroma QP mapping table and an input of the second chroma mapping table are based on the luma QP, wherein the first chroma QP mapping table for the Cb component is a separate mapping table from the second chroma QP mapping table for the Cr component.