A fiber-optic detection system for SNP analysis has been developed for monitoring the denaturation process of hybridized DNA strands on the end surface of an optical fiber. The probe DNA directly immobilized on the end surface of the fiber was hybridized to target DNA, and the denaturation process was measured. We determined the difference in melting temperature (Tm) between perfectly and SNP-matched probe-target hybrids by derivative analysis of the melting curves.