A nucleic acid detection kit comprising: (i) a first single-stranded circular DNA containing: a sequence of 10 to 30 bases complementary to a first site of a target nucleic acid; a first-primer-binding sequence of 7 to 8 bases adjacent to the 5'-side of this sequence; and a sequence complementary to a sequence that binds to a second single-stranded circular DNA; (ii) a first oligonucleotide primer containing: a sequence of 8 to 15 bases complementary to a second site adjacent to the 3'-side of the first site of the target nucleic acid; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the first-primer-binding site of the first single-stranded circular DNA; (iii) a second single-stranded circular DNA containing: the same sequence as the sequence in the first single-stranded circular DNA, complementary to the sequence that binds to the second single-stranded circular DNA; and a second-primer-binding sequence adjacent to the 5'-side of this sequence; and (iv) a second oligonucleotide primer containing: the same sequence as the site in the first single-stranded circular DNA, adjacent to the 5'-side of the sequence complementary to the sequence that binds to the second single-stranded circular DNA, wherein said same sequence as the site in the first single-stranded circular DNA is 8 to 15 bases; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the second-primer-binding sequence of the second single-stranded circular DNA, wherein the first oligonucleotide primer is bound to a carrier through the 5'-end thereof, and the second oligonucleotide primer is bound, through the 5'-end thereof, to the carrier to which the first oligonucleotide primer is bound. (i) a first single-stranded circular DNA containing: a sequence of 10 to 30 bases complementary to a first site of a target nucleic acid; a first-primer-binding sequence of 7 to 8 bases adjacent to the 5'-side of this sequence; and a sequence complementary to a sequence that binds to a second single-stranded circular DNA; a sequence of 10 to 30 bases complementary to a first site of a target nucleic acid; a first-primer-binding sequence of 7 to 8 bases adjacent to the 5'-side of this sequence; and a sequence complementary to a sequence that binds to a second single-stranded circular DNA; (ii) a first oligonucleotide primer containing: a sequence of 8 to 15 bases complementary to a second site adjacent to the 3'-side of the first site of the target nucleic acid; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the first-primer-binding site of the first single-stranded circular DNA; a sequence of 8 to 15 bases complementary to a second site adjacent to the 3'-side of the first site of the target nucleic acid; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the first-primer-binding site of the first single-stranded circular DNA; (iii) a second single-stranded circular DNA containing: the same sequence as the sequence in the first single-stranded circular DNA, complementary to the sequence that binds to the second single-stranded circular DNA; and a second-primer-binding sequence adjacent to the 5'-side of this sequence; and the same sequence as the sequence in the first single-stranded circular DNA, complementary to the sequence that binds to the second single-stranded circular DNA; and a second-primer-binding sequence adjacent to the 5'-side of this sequence; and (iv) a second oligonucleotide primer containing: the same sequence as the site in the first single-stranded circular DNA, adjacent to the 5'-side of the sequence complementary to the sequence that binds to the second single-stranded circular DNA, wherein said same sequence as the site in the first single-stranded circular DNA is 8 to 15 bases; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the second-primer-binding sequence of the second single-stranded circular DNA, wherein the first oligonucleotide primer is bound to a carrier through the 5'-end thereof, and the second oligonucleotide primer is bound, through the 5'-end thereof, to the carrier to which the first oligonucleotide primer is bound. the same sequence as the site in the first single-stranded circular DNA, adjacent to the 5'-side of the sequence complementary to the sequence that binds to the second single-stranded circular DNA, wherein said same sequence as the site in the first single-stranded circular DNA is 8 to 15 bases; and a sequence of 7 to 8 bases adjacent to the 3'-side of this sequence and complementary to the second-primer-binding sequence of the second single-stranded circular DNA, wherein the first oligonucleotide primer is bound to a carrier through the 5'-end thereof, and the second oligonucleotide primer is bound, through the 5'-end thereof, to the carrier to which the first oligonucleotide primer is bound.