1. A method performed by a video encoding apparatus for encoding a current motion vector of a current block, which is located in a current picture, the method comprising: encoding, into a bitstream, mode information for use in selecting a motion vector prediction mode among a plurality of motion vector prediction modes, wherein the plurality of motion vector prediction modes are different from each other and indicate different ways that a video decoding apparatus determines the current motion vector of the current block; and when the mode information indicating a first motion vector prediction mode among the plurality of motion vector prediction modes is encoded, performing a process comprising: deriving a set of candidate motion vectors from motion vectors of a plurality of neighboring blocks of the current block, wherein the set of candidate motion vectors is used for determining a prediction motion vector of the current block, not determining the current motion vector itself of the current block, and wherein the plurality of neighboring blocks include at least one block spatially adjacent to the current block in the current picture and at least one block in a reference picture other than the current picture, wherein a position of said at least one block in the reference picture is derived based on a position of the current block in the current picture; selecting a candidate motion vector from the set of the candidate motion vectors; setting the prediction motion vector of the current block into the selected candidate motion vector, wherein the selected candidate motion vector has been derived from said at least one block spatially adjacent block or said at least one block in a reference picture; and generating a differential motion vector of the current block by subtracting the prediction motion vector from the current motion vector, and encoding the differential motion vector into the bitstream, wherein the at least one block spatially adjacent to the current block includes one or more of blocks located at left, upper, upper right and upper left sides of the current block.