A merging motion information candidate list construction unit generates a merging motion information candidate list, which is a list of merging motion information candidates, using a spatial merging motion information candidate and a temporal merging motion information candidate. A second merging motion information candidate supplying unit generates a new merging motion information candidate including, if a reference index indicates an available reference picture, the reference index and, if the reference index does not indicate an available reference picture, a predetermined reference index along with a motion vector having a size and a direction that are preset and adds the new merging motion information candidate to the merging motion information candidate list. A merging motion information selection unit selects one merging motion information candidate from the merging motion information candidate list to which the new merging motion information candidate has been added.