A quantitative PCR probe comprising: (i) a first probe sequence hybridizable with an oligonucleotide consisting of a sequence of 10 to 35 contiguous bases in the nucleotide sequence represented by SEQ ID NO: 1 derived from the human LINE-1 gene under high stringency conditions; or (ii) a second probe sequence hybridizable with an oligonucleotide consisting of a sequence of contiguous 10 to 35 bases from within the nucleotide sequence represented by SEQ ID NO: 2 derived from the human LINE-1 gene under high stringency conditions; and a labeling part, wherein the first probe sequence of (i) is formed by any of the following to: an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 3; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 3, and wherein the second probe sequence of (ii) is formed by any of the following to: an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 6; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 6. (i) a first probe sequence hybridizable with an oligonucleotide consisting of a sequence of 10 to 35 contiguous bases in the nucleotide sequence represented by SEQ ID NO: 1 derived from the human LINE-1 gene under high stringency conditions; or (ii) a second probe sequence hybridizable with an oligonucleotide consisting of a sequence of contiguous 10 to 35 bases from within the nucleotide sequence represented by SEQ ID NO: 2 derived from the human LINE-1 gene under high stringency conditions; and a labeling part, wherein the first probe sequence of (i) is formed by any of the following to: an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 3; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 3, and an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 3; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 3; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 3, and wherein the second probe sequence of (ii) is formed by any of the following to: an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 6; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 6. an oligonucleotide consisting of the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide consisting of a nucleotide sequence that is hybridizable under high stringency conditions with the nucleotide sequence targeted by the nucleotide sequence of SEQ ID NO: 6; an oligonucleotide differing by 1 to 5 bases from the nucleotide sequence of SEQ ID NO: 6; and an oligonucleotide having 70% or more and less than 100% homology with the nucleotide sequence of SEQ ID NO: 6.