1. A hierarchical motion estimation method in which motion estimation is hierarchically performed on a macroblock, the method comprising: a first step of decimating a reference macroblock at a decimation ratio of 4:1, decimating a search window of a predetermined size at a decimation ratio of 4:1, and estimating a first motion vector responsive to the 4:1 decimated macroblock and window; a second step of decimating the reference macroblock and decimating the search window each at a decimation ratio of 2:1, and estimating at least one second motion vector responsive to the 2:1 decimated macroblock and window; and a third step of performing a full search motion estimation on a block within horizontal and vertical ranges of −N 11 to &plus;N 2 of the estimated first motion vector, estimating a third motion vector if one motion vector was estimated in the second step, or performing full search motion estimation on a block within horizontal and vertical ranges of −N 21 to &plus;N 22 of the estimated at least one second motion vector if two motion vectors were estimated in the second step.