The present disclosure provides a detection device capable of detecting a low concentration of an analyte with high sensitivity. The detection apparatus according to the present disclosure comprises a metal microstructure on which a first VHH antibody having a property of binding specifically to the analyte is immobilized and which generate surface plasmon by being irradiated with excitation light, an inlet through which a second VHH antibody and a sample that may contain an analyte are introduced, wherein the second VHH antibody has a property of binding specifically to the analyte and is labeled with a fluorescent substance, a light source for irradiating the metal microstructure to which the second VHH antibody and the sample have been introduced with the excitation light, and a detection unit for detecting the analyte on the basis of fluorescence generated from the fluorescent substance by the irradiation of the excitation light.