A moving picture decoding device that decodes a bitstream obtained by coding moving pictures using inter-prediction based on inter-prediction information of a merge candidate in units of blocks obtained by partitioning each picture of the moving pictures, comprising: a prediction information decoding unit that decodes information indicating a previously designated number of merge candidates; a prediction information deriving unit (104, 205) that derives merge candidates from inter-prediction information of a prediction block neighboring to a decoding target prediction block or a prediction block present at the same position as or near the decoding target prediction block in a decoded picture at a temporally different position from the decoding target prediction block; a candidate list constructing unit (130, 230)that constructs a merge candidate list from the derived merge candidates; a candidate generating unit (134, 234) that repeatedly performs a first process for adding to the merge candidate list a merge candidate of which the motion vector has a first value and the reference index has a second value until the number of merge candidates included in the merge candidate list reaches the designated number of merge candidates or the second value is not smaller than a variable indicating the number of reference indices when the number of merge candidates included in the merge candidate list is smaller than the designated number of merge candidates; a candidate supplementing unit (135, 235) that, after the candidate generating unit performed the first process, repeatedly performs a second process for adding to the merge candidate list a merge candidate of which the motion vector has the first value and the reference index has a third value until the number of merge candidates included in the merge candidate list reaches the designated number of merge candidates when the number of merge candidates included in the merge candidate list is smaller than the designated number of merge candidates; and a motion-compensated prediction unit (105, 206) that selects one merge candidate from the merge candidates included in the merge candidate list of which the number of merge candidates reaches the designated number of merge candidates and performs inter-prediction on the decoding target prediction block using the inter-prediction information of the selected merge candidate, wherein: the first value is (0,0); the second value is a variable that is incremented by one each time the first process occurs; and the third value is 0. a prediction information decoding unit that decodes information indicating a previously designated number of merge candidates; a prediction information deriving unit (104, 205) that derives merge candidates from inter-prediction information of a prediction block neighboring to a decoding target prediction block or a prediction block present at the same position as or near the decoding target prediction block in a decoded picture at a temporally different position from the decoding target prediction block; a candidate list constructing unit (130, 230)that constructs a merge candidate list from the derived merge candidates; a candidate generating unit (134, 234) that repeatedly performs a first process for adding to the merge candidate list a merge candidate of which the motion vector has a first value and the reference index has a second value until the number of merge candidates included in the merge candidate list reaches the designated number of merge candidates or the second value is not smaller than a variable indicating the number of reference indices when the number of merge candidates included in the merge candidate list is smaller than the designated number of merge candidates; a candidate supplementing unit (135, 235) that, after the candidate generating unit performed the first process, repeatedly performs a second process for adding to the merge candidate list a merge candidate of which the motion vector has the first value and the reference index has a third value until the number of merge candidates included in the merge candidate list reaches the designated number of merge candidates when the number of merge candidates included in the merge candidate list is smaller than the designated number of merge candidates; and a motion-compensated prediction unit (105, 206) that selects one merge candidate from the merge candidates included in the merge candidate list of which the number of merge candidates reaches the designated number of merge candidates and performs inter-prediction on the decoding target prediction block using the inter-prediction information of the selected merge candidate, wherein: the first value is (0,0); the second value is a variable that is incremented by one each time the first process occurs; and the third value is 0. the first value is (0,0); the second value is a variable that is incremented by one each time the first process occurs; and the third value is 0.