1. A motion estimator for generating an interpolation frame based on a current frame and a previous frame, the motion estimator comprising: a first candidate motion vector calculating unit which divides the current frame into a plurality of blocks and generates a plurality of first candidate motion vector groups, each of the first candidate motion vector group comprising a first candidate motion vector for each of the plurality of the blocks calculated based on a previous motion vector previously estimated; a second candidate motion vector calculating unit which calculates a plurality of second candidate motion vectors for each of the plurality of the blocks, each of the plurality of the second candidate motion vectors being calculated based on a respective first candidate motion vector included in each of the first candidate motion vector group; and a final motion vector deciding unit which selects a final motion vector for each of the plurality of the blocks from among the plurality of the second candidate motion vectors, wherein the interpolation frame is generated based on the final motion vector.