PROBLEM TO BE SOLVED: To provide a predictive vector generator that generates appropriate predictive vectors to reduce an amount of codes without adding prediction information.SOLUTION: A predictive vector generator 10 includes a similarity determining unit 101 that acquires first motion vectors of blocks adjacent to a block to be encoded and second motion vectors of blocks adjacent to a reference block identical in position to the block to be encoded in a reference picture referred by the block to be encoded, and that determines whether the locations of the first and second motion vectors have similarity, a horizontal edge determining unit 102 that, when both types of motion vectors are determined to have similarity, determines whether a horizontal edge exists on the basis of the locations of the second motion vectors and a motion vector of the reference block, and a predictive vector determining unit 103 that, when the horizontal edge is determined to exist, determines, as a predictive vector, the first motion vector of the block, which is horizontally adjacent to the block to be encoded, while when the both types of motion vectors are determined not to have similarity or the horizontal edge is determined not to exist, determines, as the predictive vector, a median or average of the first motion vectors.