An apparatus for decoding a video, the apparatus comprising: a parser which obtains, from a received bitstream, a skip flag for a coding unit which indicates whether a encoding mode for the coding unit is a skip mode, and, when the skip flag indicates a non-skip mode, obtains, from the bitstream, information about a partition type for prediction and determining at least one partition from the coding unit using the information about a partition type and obtains a merge flag for the partition, from the received bitstream; and a motion information obtainer which, when the merge flag for the partition indicates a merge mode, obtains merge index for the partition and determining motion information for the partition using motion information of a block which the merge index indicates, and, when the merge flag for the partition indicates a non-merge mode, obtains motion information for the partition from the bitstream; and a data decoder which, when the merge flag for the partition indicates a merge mode, performs motion compensation on the partition using the determined motion information of the block which the merge index indicates, and, when the merge flag for the partition indicates a non-merge mode, performs motion compensation on the partition using the obtained motion information, characterized in that the merge index indicates one block among a merge candidate block group comprising one or more blocks from among the following three_neighboring blocks of the partition: a left-lower block located on a left side of a leftmost block among lower blocks directly below a lower border of the partition, a left-upper block located on a left side of a leftmost block among upper blocks directly above an upper border of the partition, the left-upper block being located above an uppermost block among the left blocks adjacent to the left border of the partition, 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 partition. a parser which obtains, from a received bitstream, a skip flag for a coding unit which indicates whether a encoding mode for the coding unit is a skip mode, and, when the skip flag indicates a non-skip mode, obtains, from the bitstream, information about a partition type for prediction and determining at least one partition from the coding unit using the information about a partition type and obtains a merge flag for the partition, from the received bitstream; and a motion information obtainer which, when the merge flag for the partition indicates a merge mode, obtains merge index for the partition and determining motion information for the partition using motion information of a block which the merge index indicates, and, when the merge flag for the partition indicates a non-merge mode, obtains motion information for the partition from the bitstream; and a data decoder which, when the merge flag for the partition indicates a merge mode, performs motion compensation on the partition using the determined motion information of the block which the merge index indicates, and, when the merge flag for the partition indicates a non-merge mode, performs motion compensation on the partition using the obtained motion information, characterized in that the merge index indicates one block among a merge candidate block group comprising one or more blocks from among the following three_neighboring blocks of the partition: a left-lower block located on a left side of a leftmost block among lower blocks directly below a lower border of the partition, a left-upper block located on a left side of a leftmost block among upper blocks directly above an upper border of the partition, the left-upper block being located above an uppermost block among the left blocks adjacent to the left border of the partition, 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 partition. a left-lower block located on a left side of a leftmost block among lower blocks directly below a lower border of the partition, a left-upper block located on a left side of a leftmost block among upper blocks directly above an upper border of the partition, the left-upper block being located above an uppermost block among the left blocks adjacent to the left border of the partition, 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 partition.