1. A method of determining the quality of Heart & Cupid optical effects of a diamond, including the steps of: reading out dimensions, which have been obtained by measuring a round brilliant cut diamond with an ID appended using a dimension measuring device, by computer graphics and outputting Heart & Cupid images and the ID or outputting Heart & Cupid images of the diamond taken by a CCD camera and an ID; storing symmetry data of eight heart marks, namely variation in area of a heart, displacement of a tip portion of each of a heart, the depth of a slit of each heart, a ratio of right and left shoulder widths relative to overall width of each heart, a ratio of a distance in a boundary portion between each heart and a V-shaped mark located on an inner side on a radial line of the heart relative to the overall width of the corresponding heart, a ratio between area of the V-shaped mark and area of a standard heart, and a ratio between right-side length of the V-shaped mark and left-side length of the V-shaped mark, into a computer database; determining ranking of quality of the eight heart marks by performing arithmetic processing of the symmetry data of eight heart marks; and storing said symmetry data of eight cupid marks, namely, a variation in degree obtained from a ratio between a maximum value and a minimum value of each cupid area, whether a straight line connecting an outer tip portion, an intermediate intersection, and a center-side tip of each cupid overlaps another straight line or has a displacement with an angle, and whether an arrow tip portion of each cupid sharply abuts against a girdle or abuts against a girdle portion with a width, into a computer database and determining ranking of quality of the symmetry data of the eight cupid marks by performing arithmetic processing of the symmetry data of eight cupid marks and determining quality ranking by converting into numbers the symmetry data of each heart mark and each cupid mark, by a computer, and performing determination processing by using said computer, wherein ranking determination includes three determined areas where an approved area, a disapproved area, and approved and disapproved areas are present or two determined areas where an approved area and a disapproved area are present.