During inter-prediction, whereby a first block having each picture divided therein is divided into one or a plurality of second blocks, a spatial merge candidate generation unit (130) derives spatial merge candidates, without referring to blocks included in the first block, including the second block. A reference index derivation unit (131) for temporal merge candidates: sets reference index information for a temporal merge candidate as the value for reference index information for an encoded prediction block approaching the left side of a prediction block for encoding, when in a mode whereby the encoded block is divided into upper and lower prediction blocks at the horizontal interface; and sets reference index information for a temporal merge candidate as the value for reference index information for an encoded prediction block approaching the top side of the prediction block for encoding, when in a mode whereby the encoded block is divided into left and right prediction blocks at the vertical interface.
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