1. A moving picture decoding device adapted to decode a bitstream in which moving pictures are coded in units of blocks obtained by partitioning each picture of the moving pictures, comprising: a motion vector predictor candidate generation unit configured to derive one or more motion vector predictor candidates from motion vectors of decoded prediction blocks neighboring a prediction block subject to decoding within the same picture as the prediction block subject to decoding, and to add the derived motion vector predictor candidates in a motion vector predictor candidate list; a decoding unit configured to decode index information indicating the motion vector predictor candidate that should be selected in the motion vector predictor candidate list and motion vector difference; a motion vector predictor selection unit configured to select a motion vector predictor from the motion vector predictor candidate list, based on the decoded index information indicating the motion vector predictor that should be selected; and a motion vector derivation unit configured to derive a motion vector by adding the motion vector difference to the selected motion vector predictor, wherein the motion vector predictor candidate generation unit determines, for the purpose of obtaining a predetermined number of motion vector predictor candidates, which of the decoded prediction blocks provides the motion vector from which to derive the motion vector predictor candidate, such that the motion vector predictor candidate generation unit processes, in a predetermined order, prediction blocks in a block group neighboring to the left and in a block group neighboring above, said processing being done according to conditions 1 and 2 below in the stated order and then according to conditions 3 and 4 below in the stated order, condition 1: there is found a motion vector that is predicted by using the same reference list and the same reference picture as that of the motion vector predictor subject to derivation in the prediction block subject to decoding; condition 2: there is found a motion vector that is predicted by using a reference list different from that of the motion vector predictor subject to derivation in the prediction block subject to decoding and using the same reference picture as that of the motion vector predictor subject to derivation in the prediction block subject to decoding; condition 3: there is found a motion vector that is predicted by using the same reference list as that of the motion vector predictor subject to derivation in the prediction block subject to decoding and using a reference picture different from that of the motion vector predictor subject to derivation in the prediction block subject to decoding; and condition 4: there is found a motion vector that is predicted by using a reference list different from that of the motion vector predictor subject to derivation in the prediction block subject to decoding and using a reference picture different from that of the motion vector predictor subject to derivation in the prediction block subject to decoding.