1. A motion estimation method, adapted to a motion estimation device, the motion estimation method comprising: dividing a first frame to be estimated into a plurality of area units, wherein each of the area units comprises a plurality of blocks; and assigning a set of motion vector values to each of the area units, wherein the set of motion vector values comprises a plurality of predetermined motion vector values, and each of the predetermined motion vector values is assigned to at least one block in each of the area units, wherein each of the area units of the first frame to be estimated has one sub-area or multiple sub-areas, each of the sub-areas comprises one block or multiple blocks, and the one block or the multiple blocks of two corresponding sub-areas in any two area units are respectively assigned the same predetermined motion vector values with a rotation mapping relationship.