The present invention relates to a novel method for detecting a target polynucleotide having a target sequence, comprising hybridizing the target polynucleotide with a probe to form a hybrid; exposing the hybrid to a 5′ exonuclease so that the probe in the hybrid is digested and the target polynucleotide is dissociated from the digested probe; repeating the hybridization step and the digestion step; and detecting the digested probes. The presence of the digested probes indicates the presence of the target polynucleotide.