This invention provides a simple detection method with excellent sensitivity and specificity, which allows prompt detection of an analyte by allowing a labeled reagent to effectively react with the analyte in the process of treating an analyte-containing specimen, such as during removal of impurities, a detection apparatus, and a detection kit. This method for detecting an analyte in specimens comprises steps of: bringing a labeled reagent containing a ligand that specifically binds to the analyte into contact with a specimen; and supplying the mixture of the specimen and the labeled reagent to a solid-phase support onto which a capture reagent that specifically binds to the analyte has been immobilized, wherein the step of bringing the specimen into contact with the labeled reagent is carried out at a site that is not on the solid-phase support and that is detached from the solid-phase support. The invention also provides a detection apparatus comprising a solid-phase support onto which a capture reagent that specifically binds to the analyte in the specimen is immobilized and a kit for detecting an analyte in a specimen and a device for supplying a specimen comprising a labeled reagent containing a ligand that specifically binds to the analyte.