1. An apparatus for encoding a motion vector, the apparatus comprising: a predicted motion vector candidate aggregator for aggregating predicted motion vector candidates of a current block into a plurality of groups; a representative predicted motion vector selector for selecting representative predicted motion vectors for respective groups by selecting one predicted motion vector candidate from aggregated predicted motion vector candidates within the respective groups as a representative predicted motion to vector; a predicted motion vector selector for selecting a single representative predicted motion vector from the representative predicted motion vectors for the respective groups as a predicted motion vector; and a differential vector encoder for encoding a differential vector representing is a difference between a current motion vector of the current block and a selected predicted motion vector.