Provided is a method extracts a merge index from a bit stream, constructs a merge candidate list using available spatial and temporal merge candidates, selects a merge predictor among merge candidates using the merge index, and sets motion information of the merge predictor as motion information of the current prediction unit. The temporal merge candidate includes a reference picture index and a motion vector, and a motion vector of a temporal merge candidate block of a temporal merge candidate picture is set as the motion vector of the temporal merge candidate. Accordingly, the coding efficiency of the motion information is improved by including various merge candidates. Also, the computational complexity of an encoder and a decoder is reduced maintaining improvement of coding efficiency by adaptively storing motion information of reference picture and adaptively generating a temporal merge candidate.