Provided is a detection method including exposing, to contact with a surface to which a cofactor has been bound, a nuclear receptor protein serving as a counterpart of the cofactor and a test sample; and detecting a substance which is contained in the test sample and which binds to the nuclear receptor, on the basis of a change in degree of binding between the nuclear receptor protein and the cofactor. The detection method is means for detecting a living-body-related substance, which means employs a nuclear receptor-cofactor system, exhibits detection high sensitivity, provides a convenient detection process, and realizes efficient establishment of a detection system.