A picture decoding method comprising: decoding a coded image signal to obtain: a reference index that identifies a reference picture for a current block to be decoded; commands that indicate correspondence between reference indices and reference pictures; information that indicates a maximum reference index value; a plurality of weighting coefficient sets used for generating a predictive image; and a prediction error; designating, based on the commands and the reference index, a reference picture which is referred to when the current block is decoded through motion compensation; specifying a weighting coefficient set corresponding to the reference index, from among the plurality of weighting coefficient sets; generating the predictive image by performing linear prediction, using the specified weighting coefficient set, on pixel values of a reference block obtained from the reference picture designated in said designating; and generating a reconstructed image from the predictive image and the prediction error, wherein each of the plurality of weighting coefficient sets is specified by a corresponding one of the plurality of reference indices, wherein, in said specifying, a weighting coefficient set corresponding to the reference index which is obtained through decoding the current block, from among the at least two weighting coefficient sets, is specified, and wherein said performing linear prediction further comprises: scaling the pixel values of the reference block with a first part w1 of the specified weighting coefficient set, and increasing the scaled pixel values of the reference block by a second part c1 of the specified weighting coefficient set, characterized in that at least two reference indices among the plurality of reference indices are assigned to one reference picture in the commands, and at least two weighting coefficient sets among the plurality of weighting coefficient sets are assigned to said one reference picture. decoding a coded image signal to obtain: a reference index that identifies a reference picture for a current block to be decoded; commands that indicate correspondence between reference indices and reference pictures; information that indicates a maximum reference index value; a plurality of weighting coefficient sets used for generating a predictive image; and a prediction error; designating, based on the commands and the reference index, a reference picture which is referred to when the current block is decoded through motion compensation; specifying a weighting coefficient set corresponding to the reference index, from among the plurality of weighting coefficient sets; generating the predictive image by performing linear prediction, using the specified weighting coefficient set, on pixel values of a reference block obtained from the reference picture designated in said designating; and generating a reconstructed image from the predictive image and the prediction error, wherein each of the plurality of weighting coefficient sets is specified by a corresponding one of the plurality of reference indices, wherein, in said specifying, a weighting coefficient set corresponding to the reference index which is obtained through decoding the current block, from among the at least two weighting coefficient sets, is specified, and wherein said performing linear prediction further comprises: scaling the pixel values of the reference block with a first part w1 of the specified weighting coefficient set, and increasing the scaled pixel values of the reference block by a second part c1 of the specified weighting coefficient set, scaling the pixel values of the reference block with a first part w1 of the specified weighting coefficient set, and increasing the scaled pixel values of the reference block by a second part c1 of the specified weighting coefficient set, characterized in that at least two reference indices among the plurality of reference indices are assigned to one reference picture in the commands, and at least two weighting coefficient sets among the plurality of weighting coefficient sets are assigned to said one reference picture.