A method of deriving a temporal prediction motion vector, the method being performed by a video decoding apparatus, the method comprising: deriving reference picture index information relating to a prediction target block from video data, the reference picture index information being used to determine a collocated picture of the prediction target block; determining, based on the reference picture index information, the collocated picture among a plurality of decoded pictures; determining, from among a first collocated block and a fifth collocated block, a collocated block of the prediction target block to be predicted based on the temporal prediction motion vector, wherein the prediction target block is included in a current picture and wherein the first collocated block and the fifth collocated block are included in the collocated picture; and deriving the temporal prediction motion vector based on a motion vector of the determined collocated block, wherein determining the collocated block comprises: determining whether a lower boundary of the prediction target block adjoins with a lower boundary of a Largest Coding Unit, LCU wherein the prediction target block is located within the LCU; determining, based on the determination of whether the lower boundary of the prediction target block adjoins with the lower boundary of the LCU, an availability of the first collocated block; and determining, based on the availability of the first collocated block, one of the first collocated block and the fifth collocated block to be the collocated block; wherein when the lower boundary of the prediction target block adjoins with the lower boundary of the LCU, the first collocated block is determined to be unavailable and the available fifth collocated block, instead of the unavailable first collocated block, is determined to be the collocated block, wherein if a location of a point at a top-left of the prediction target block is (xP, yP), a width of the prediction target block is nPSW, and a height of the prediction target block is nPSH, the first collocated block is a block including a point at (xP+nPSW, yP+nPSH) within the collocated picture, and the fifth collocated block is a block including a point at (xP+(nPSW>>1), yP+(nPSH>>1)) within the collocated picture. deriving reference picture index information relating to a prediction target block from video data, the reference picture index information being used to determine a collocated picture of the prediction target block; determining, based on the reference picture index information, the collocated picture among a plurality of decoded pictures; determining, from among a first collocated block and a fifth collocated block, a collocated block of the prediction target block to be predicted based on the temporal prediction motion vector, wherein the prediction target block is included in a current picture and wherein the first collocated block and the fifth collocated block are included in the collocated picture; and deriving the temporal prediction motion vector based on a motion vector of the determined collocated block, wherein determining the collocated block comprises: determining whether a lower boundary of the prediction target block adjoins with a lower boundary of a Largest Coding Unit, LCU wherein the prediction target block is located within the LCU; determining, based on the determination of whether the lower boundary of the prediction target block adjoins with the lower boundary of the LCU, an availability of the first collocated block; and determining, based on the availability of the first collocated block, one of the first collocated block and the fifth collocated block to be the collocated block; wherein when the lower boundary of the prediction target block adjoins with the lower boundary of the LCU, the first collocated block is determined to be unavailable and the available fifth collocated block, instead of the unavailable first collocated block, is determined to be the collocated block, determining whether a lower boundary of the prediction target block adjoins with a lower boundary of a Largest Coding Unit, LCU wherein the prediction target block is located within the LCU; determining, based on the determination of whether the lower boundary of the prediction target block adjoins with the lower boundary of the LCU, an availability of the first collocated block; and determining, based on the availability of the first collocated block, one of the first collocated block and the fifth collocated block to be the collocated block; wherein if a location of a point at a top-left of the prediction target block is (xP, yP), a width of the prediction target block is nPSW, and a height of the prediction target block is nPSH, the first collocated block is a block including a point at (xP+nPSW, yP+nPSH) within the collocated picture, and the fifth collocated block is a block including a point at (xP+(nPSW>>1), yP+(nPSH>>1)) within the collocated picture.