There is provided a method and apparatus for encoding and decoding motion vectors. Motion vectors are encoded through the steps of: (a) predicting motion vectors of a type identical to that of a present block and obtaining predictive motion vectors with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block; (b) calculating a representative value of the motion vectors of the type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vectors; (c) calculating a difference value between the calculated representative value and the motion vector of the present block; and (d) encoding the calculated difference value. The motion vectors can be more efficiently encoded even when they refer to different reference pictures.