The present invention relates to a method capable of, in order to diagnose fetal sex chromosome aneuploidy, differentiating Kleinfeiter's syndrome (XXY), triple X syndrome (XXX), and Turner's syndrome (monosomy X, XO) as well as male (XY) and female (XX) by using copy number variation (CNV). The differentiation method according to the present invention has significantly high sensitivity and accuracy since the reference line is evenly adjusted by performing normalization regardless of the kinds of platform and data. The present invention is useful in diagnosing the sex chromosome abnormality at an early stage through easy diagnosis of sex chromosomes X and Y, which are hard to diagnose, since an analysis is possible even with a small amount of fetal chromosomes, which corresponds to an advantage of noninvasive prenatal diagnosis, and copies are redundant.