To provide a DNA micro-array having a nucleic acid probe immobilized on a substrate, which is used to detect a molecule of a target nucleic acid contained in a sample and has a substantially complementary base sequence to the target base sequence of the nucleic acid molecule, including at least one probe selected from the group consisting of: at least one internal standard probe for assay of PCR of the target nucleic acid; at least one external standard probe for a detection operation and assay of an amount of the probe; and a probe for measurement of the amount or density of the nucleic acid probe, formed by the same method as the nucleic acid probe.