1. A video decoder comprising: an entropy-decoding unit which performs entropy-decoding for obtaining a residual block, information on motion vector difference, and partition information from an encoded bitstream; a motion vector estimation unit which selects at least one of partitions from among a plurality of candidate partitions around a current block and a candidate partition located in a position in a reference picture that spatially corresponds to the position of the current block, based on the partition information indicating the selected at least one of partitions, estimates a motion vector of the current block based on a motion vector of the selected at least one of partitions, and adds the decoded motion vector difference to the estimated motion vector of the current block in order to reconstruct the motion vector of the current block; and a block reconstruction unit which reconstructs the current block from the decoded residual block using the reconstructed motion vector, wherein the plurality of candidate partitions around the current block are located in a left side or an upper side of the current block.