Abstract: Disclosed is a new technology for use in gene diagnosis, which enables simple and highly sensitive detection of an abnormal gene. A nucleic acid oligomer having a base sequence of a normal gene of interest is hybridized in a reversed micelle with a probe having a base sequence complementary to said base sequence of the normal gene; the nucleic acid oligomer having the base sequence of the normal gene is hybridized in another reversed micelle with a probe having a base sequence complementary to a base sequence of an abnormal gene partly altered from the base sequence of the normal gene; and the rates of the hybridization reactions are measured to examine the difference therebetween. The rates of the hybridization reactions can be measured, for example, by measuring change in ultraviolet light absorbance.