A method for detecting one or more target nucleic acids present in a sample, comprising the following steps: adding a fluorophore-labeled primer or probe and a quencher-labeled probe to the sample, or adding the sample to a fluorophore-labeled primer or probe and a quencher-labeled probe, wherein the fluorophore-labeled primer or probe is a fluorophore-labeled oligonucleotide having complementarity to a target nucleic acid, and the quencher-labeled probe is a quencher-labeled oligonucleotide having complementarity to the fluorophore-labeled primer or probe and having a melting temperature (Tm) lower than that of the fluorophore-labeled primer or probe; incubating the sample at a temperature equal to or lower than the melting temperature (Tm) of the fluorophore-labeled primer or probe and higher than the melting temperature (Tm) of the quencher-labeled probe wherein the target nucleic acid is amplified under isothermal conditions by isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN), strand displacement amplification, rolling circle amplification, smart amplification process version 2 (SMAP2) or loop-mediated isothermal amplification (LAMP); annealing the fluorophore-labeled primer or probe that is unannealed to the target nucleic acid, to the quencher-labeled probe by incubating the sample at a temperature equal to or lower than the melting temperature (Tm) of the quencher-labeled probe, thereby quenching the fluorescence emitted by the fluorophore-labeled primer or probe unannealed to the target nucleic acid by the quencher; and measuring fluorescence of the fluorophore-labeled primer or probe bound with the target nucleic acid, while the sample is kept at a temperature equal to or lower than the melting temperature (Tm) of the quencher-labelled probe, wherein only the fluorescent labels in the fluorophore-labeled primer or probe successfully bound with the target nucleic acid can be detected. adding a fluorophore-labeled primer or probe and a quencher-labeled probe to the sample, or adding the sample to a fluorophore-labeled primer or probe and a quencher-labeled probe, wherein the fluorophore-labeled primer or probe is a fluorophore-labeled oligonucleotide having complementarity to a target nucleic acid, and the quencher-labeled probe is a quencher-labeled oligonucleotide having complementarity to the fluorophore-labeled primer or probe and having a melting temperature (Tm) lower than that of the fluorophore-labeled primer or probe; incubating the sample at a temperature equal to or lower than the melting temperature (Tm) of the fluorophore-labeled primer or probe and higher than the melting temperature (Tm) of the quencher-labeled probe wherein the target nucleic acid is amplified under isothermal conditions by isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN), strand displacement amplification, rolling circle amplification, smart amplification process version 2 (SMAP2) or loop-mediated isothermal amplification (LAMP); annealing the fluorophore-labeled primer or probe that is unannealed to the target nucleic acid, to the quencher-labeled probe by incubating the sample at a temperature equal to or lower than the melting temperature (Tm) of the quencher-labeled probe, thereby quenching the fluorescence emitted by the fluorophore-labeled primer or probe unannealed to the target nucleic acid by the quencher; and measuring fluorescence of the fluorophore-labeled primer or probe bound with the target nucleic acid, while the sample is kept at a temperature equal to or lower than the melting temperature (Tm) of the quencher-labelled probe, wherein only the fluorescent labels in the fluorophore-labeled primer or probe successfully bound with the target nucleic acid can be detected.