A method of generating a prediction block using a merge mode, the method comprising: generating a quantized block by inverse-scanning quantized coefficient components; generating a transformed block by inverse-quantizing the quantized block using a quantization parameter; generating a residual block by inverse-transforming the transformed block; constructing a merge list using available spatial and temporal merge candidates, wherein each of the spatial and temporal merge candidates comprises motion information which includes a motion vector and a reference picture index; setting a merge candidate on the merge list specified by a merge index as motion information of a current block; generating a prediction block of the current block using the motion information; and generating a reconstructed block using the prediction block and the residual block, wherein, in the operation of constructing the merge list, wherein when the current prediction unit is a second prediction unit partitioned from a current coding unit by asymmetric partitioning, the spatial merge candidate block corresponding to a first prediction unit partitioned from the current coding unit by the asymmetric partitioning is set as unavailable, a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate block within a temporal merge candidate picture, wherein one temporal merge candidate picture is used within a slice, the temporal merge candidate block is determined based on a position of the current block, wherein a first temporal merge candidate block is a block right-below the corner of a block having the same size and location of the current block and being located within the temporal merge candidate picture when the first temporal merge candidate block is available, wherein the first temporal merge candidate block is not available when the first temporal merge candidate block belongs to an adjacent lower largest coding unit, LCU, and a reference picture index and a motion vector of a current block are a reference picture index and a motion vector of a merge candidate specified by the merge index, wherein the reference picture index of the temporal merge candidate is set as 0. generating a quantized block by inverse-scanning quantized coefficient components; generating a transformed block by inverse-quantizing the quantized block using a quantization parameter; generating a residual block by inverse-transforming the transformed block; constructing a merge list using available spatial and temporal merge candidates, wherein each of the spatial and temporal merge candidates comprises motion information which includes a motion vector and a reference picture index; setting a merge candidate on the merge list specified by a merge index as motion information of a current block; generating a prediction block of the current block using the motion information; and generating a reconstructed block using the prediction block and the residual block, wherein, in the operation of constructing the merge list, wherein when the current prediction unit is a second prediction unit partitioned from a current coding unit by asymmetric partitioning, the spatial merge candidate block corresponding to a first prediction unit partitioned from the current coding unit by the asymmetric partitioning is set as unavailable, a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate block within a temporal merge candidate picture, wherein one temporal merge candidate picture is used within a slice, the temporal merge candidate block is determined based on a position of the current block, wherein a first temporal merge candidate block is a block right-below the corner of a block having the same size and location of the current block and being located within the temporal merge candidate picture when the first temporal merge candidate block is available, wherein the first temporal merge candidate block is not available when the first temporal merge candidate block belongs to an adjacent lower largest coding unit, LCU, and a reference picture index and a motion vector of a current block are a reference picture index and a motion vector of a merge candidate specified by the merge index, wherein the reference picture index of the temporal merge candidate is set as 0. wherein when the current prediction unit is a second prediction unit partitioned from a current coding unit by asymmetric partitioning, the spatial merge candidate block corresponding to a first prediction unit partitioned from the current coding unit by the asymmetric partitioning is set as unavailable, a motion vector of the temporal merge candidate is a motion vector of a temporal merge candidate block within a temporal merge candidate picture, wherein one temporal merge candidate picture is used within a slice, the temporal merge candidate block is determined based on a position of the current block, wherein a first temporal merge candidate block is a block right-below the corner of a block having the same size and location of the current block and being located within the temporal merge candidate picture when the first temporal merge candidate block is available, wherein the first temporal merge candidate block is not available when the first temporal merge candidate block belongs to an adjacent lower largest coding unit, LCU, and a reference picture index and a motion vector of a current block are a reference picture index and a motion vector of a merge candidate specified by the merge index, wherein the reference picture index of the temporal merge candidate is set as 0.