A method for encoding or decoding an image signal according to the present invention may comprise the steps of: determining a plurality of weight prediction parameter candidates for a coding block based on number information signaled in a unit of a sequence of a bitstream, the sequence being a higher unit of the coding block, determining a weight prediction parameter of the coding block from the weight prediction parameter candidates based on index information signaled in the unit of the coding block, and obtaining a prediction block of the coding block by obtaining a second prediction sample of the coding block.