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; a maximum value of reference indices; commands that indicate correspondence between the reference indices and reference pictures; 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 the plurality of weighting coefficient sets used for generating the predictive image are placed in a slice header of the coded image signal, and wherein the current block is a block included in a P picture and the current block is decoded by designating one reference picture which is referred to, and each of the plurality of weighting coefficient sets comprises a first part w1 and a second part c1, the first part w1 being used for scaling pixel values of the reference block and the second part c1 being used for increasing each of the scaled pixel values by a value of c1, and characterized in that at least two reference indices are assigned to the one reference picture referred to by the current block and the one reference picture referred to by the current block is designated by the one reference index of the at least two reference indices. decoding a coded image signal to obtain: a reference index that identifies a reference picture for a current block to be decoded; a maximum value of reference indices; commands that indicate correspondence between the reference indices and reference pictures; 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 the plurality of weighting coefficient sets used for generating the predictive image are placed in a slice header of the coded image signal, and wherein the current block is a block included in a P picture and the current block is decoded by designating one reference picture which is referred to, and each of the plurality of weighting coefficient sets comprises a first part w1 and a second part c1, the first part w1 being used for scaling pixel values of the reference block and the second part c1 being used for increasing each of the scaled pixel values by a value of c1, and characterized in that at least two reference indices are assigned to the one reference picture referred to by the current block and the one reference picture referred to by the current block is designated by the one reference index of the at least two reference indices.