1. An apparatus for decoding a video, the apparatus comprising: a processor which is configured for obtaining, from a bitstream, split information for a coding unit, and a decoder which determines one or more partitions from the coding unit, when the split information indicates a non-split for the coding unit, obtaining, from the bitstream, a skip flag for the coding unit which indicates whether a prediction mode for the coding unit is a skip mode, when the skip flag indicates the skip mode, obtaining, from the bitstream, a merge index indicating one block among a candidate block group, and determining a motion vector of the coding unit based on a motion vector of the one block indicated by the merge index, and when the skip flag indicates a non-skip mode, obtaining, from the bitstream, a partition type and merge information of a partition, wherein: the candidate block group includes three or more blocks among neighboring blocks of the coding unit, the neighboring blocks comprising: a left-lower block located on a left side of a leftmost block among lower blocks directly below a lower border of a prediction unit in the coding unit, the left-lower block being located below a lowermost block among left blocks adjacent to a left border of the prediction unit, a left-upper block located on a left side of a leftmost block among upper blocks directly above an upper border of the prediction unit, the left-upper block being located above an uppermost block among the left blocks adjacent to the left border of the prediction unit, and a right-upper block located on a right side of a rightmost block among the upper blocks directly above the upper border of the prediction unit; when the partition type is obtained from the bitstream, the decoder determines one or more partitions, including the partition, from the coding unit based on the partition type, the merge information of the partition indicates whether the partition among the one or more partitions is decoded in a merge mode, when the split information indicates a split for a current depth, the coding unit of the current depth is split into four rectangular coding units of a lower depth, independently from neighboring coding units, and when the split information indicates a non-split of the current depth, the one or more partitions are obtained from the coding unit of the current depth when the skip flag indicates the non-skip mode, and one or more transformation units are obtained from the coding unit of the current depth.