1. A video decoder comprising: an entropy-decoding unit which performs entropy-decoding on 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 neighboring partitions around a current block based on the spatial similarities between the current block and the plurality of neighboring partitions, estimates a motion vector of the selected partition as the motion vector of the current block, 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 macroblock reconstruction unit which reconstructs the current block from the decoded residual block using the reconstructed motion vector.