1. An inter prediction method comprising: generating a merging candidate list of a block to be predicted and corresponding to a current prediction unit (PU); deriving motion information of the block to be predicted, on the basis of one of a plurality of merging candidates constituting the merging candidate list; and performing a prediction on the block to be predicted, on the basis of the derived motion information, to generate a prediction block corresponding to the current PU, wherein the current PU is a PU belonging to a merging candidate sharing unit, and wherein in the generating of the merging candidate list, one of a first merging candidate list consisting of a plurality of first merging candidates and a second merging candidate list consisting of a plurality of second merging candidates is selectively generated, the plurality of first merging candidates are motion information of a plurality of first blocks determined based on a location and size of the block to be predicted, and the plurality of second merging candidates are motion information of a plurality of second blocks determined based on a location and size of a block corresponding to the merging candidate sharing unit.