1. A motion vector detection system having a motion vector detector for obtaining a motion vector of a block to be predicted in a frame subjected to prediction through block matching of the block to be predicted and a search block within a search range in a reference frame, and a motion vector memory for storing the motion vector obtained in the motion vector detector being mapped onto a position of the block to be predicted, the motion vector detection system comprising: a predicted motion vector calculator for retrieving individual motion vectors of a plurality of reference blocks adjacent to the position of the block to be predicted from the motion vector memory and calculating a predicted motion vector predicting the motion vector of the block to be predicted based upon the individual motion vectors of the plurality of reference blocks retrieved; and a search range determiner for determining the search range in the reference frame based upon the predicted motion vector.