A set for use for at least confirming the presence or absence of contamination of a container for a test sample with a positive control nucleic acid in the detection or quantification of a target nucleic acid in a test sample using a primer set specific for the target nucleic acid and a probe specific for the target nucleic acid, the set comprising a positive control nucleic acid and a probe specific for the positive control nucleic acid, wherein the positive control nucleic acid serves as a positive control of the target nucleic acid and is any one of a nucleic acid selected from (I) a single-stranded nucleic acid consisting of a nucleotide sequence having the following features (A) to (D), (II) a single-stranded nucleic acid consisting of a nucleotide sequence complementary to the nucleotide sequence of the single-stranded nucleic acid (I), and (III) a double-stranded nucleic acid formed from the single-stranded nucleic acid (I) and the single-stranded nucleic acid (II), wherein the positive control nucleic acid can be amplified using the primer set specific for the target nucleic acid, wherein the nucleotide sequence of the probe specific for the positive control nucleic acid is a nucleotide sequence that has 70% or lower sequence identity to the sequence of any portion of the genomes of an organism species from which the test sample is derived and an organism species from which the target nucleic acid is derived, and transcripts thereof, and has a Tm value of 65°C or lower; and wherein the nucleotide sequence of the probe specific for the positive control nucleic acid is a nucleotide sequence that has 70% or lower sequence identity to the sequence of any portion of the genomes of 20 or more species selected from the group consisting of mammals, bacteria, fungi and viruses, and transcripts thereof, and has a Tm value of 65°C or lower: (A) comprising a nucleotide sequence A1 of a 5' primer specific for the target nucleic acid and a nucleotide sequence A2 complementary to a 3' primer specific for the target nucleic acid; (B) comprising a nucleotide sequence B1 complementary to the probe specific for the target nucleic acid, or a nucleotide sequence B2 complementary to the nucleotide sequence B1; (C) comprising a nucleotide sequence C1 complementary to the probe specific for the positive control nucleic acid, or a nucleotide sequence C2 complementary to the nucleotide sequence C1; and (D) the nucleotide sequence B1 or B2 and the nucleotide sequence C1 or C2 are positioned between the nucleotide sequences A1 and A2. (A) comprising a nucleotide sequence A1 of a 5' primer specific for the target nucleic acid and a nucleotide sequence A2 complementary to a 3' primer specific for the target nucleic acid; (B) comprising a nucleotide sequence B1 complementary to the probe specific for the target nucleic acid, or a nucleotide sequence B2 complementary to the nucleotide sequence B1; (C) comprising a nucleotide sequence C1 complementary to the probe specific for the positive control nucleic acid, or a nucleotide sequence C2 complementary to the nucleotide sequence C1; and (D) the nucleotide sequence B1 or B2 and the nucleotide sequence C1 or C2 are positioned between the nucleotide sequences A1 and A2. <EOS>