The present invention addresses the problem of improving separation performance in separating a hybrid of a mutant-type DNA and a probe or/and a hybrid of a wild-type type DNA and a probe, said hybrids being obtained by the LH method. The present invention relates to "a method for detection of mutant-type DNA or/and wild-type DNA which comprises the following steps: (1) a step in which at least one of a single-stranded DNA having a substituted nucleotide, a deficient nucleotide region, or an inserted nucleotide region (mutant-type DNA), or/and a wild-type single-stranded DNA corresponding to the mutant-type DNA (wild-type DNA) is contacted with a probe hybridizing with both single-stranded DNAs, to form a hybrid with the mutant-type DNA (mutant-type hybrid) or/and a hybrid with the wild-type DNA (wild-type hybrid) (in this regard however, at least one of the obtained mutant-type hybrid and wild-type hybrid has a loop structure), (2) a step in which the obtained mutant-type hybrid or/and wild-type hybrid is contacted with an intercalator, and (3) a step in which the presence or absence of the mutant-type DNA or/and the wild-type DNA is detected by separating the conjugate of mutant-type hybrid and intercalator or/and the conjugate of wild-type hybrid and intercalator".