1. A pattern extracting apparatus which is applied to a charge-particle beam exposure system for extracting an input exposure pattern corresponding to a unit block exposure pattern, the input exposure pattern including a plurality of apexes, a selected apex of the input exposure pattern having first vectors connecting the selected apex to other apexes of the input exposure pattern, the unit block exposure pattern including a plurality of apexes, one of the plurality of apexes of the unit block exposure pattern being a reference point having second vectors connecting the reference point to other apexes of the unit block exposure pattern, said pattern extracting apparatus comprising: comparator means for comparing the first vectors of the selected apex of the input exposure pattern with the second vectors of the reference point of the unit block exposure pattern; determining means, coupled to said comparator means, for determining whether or not the first vectors coincide with the second vectors; and extracting means, coupled to the determining means, for extracting the input exposure pattern as the unit block exposure pattern when the determining means determines that the first vectors coincide with the second vectors.