A method of detecting analytes, comprising the steps of: putting receptors into a sample containing the analytes to thus induce the receptors and the analytes to be coupled with each other, and to thereby form analyte-receptor complexes that are obtained by a coupling of the receptors with the analytes, respectively; separating the analyte-receptor complexes from free receptors that have not been coupled with the analytes; and wherein the receptors are used at a state being immobilized with fluorescent-magnetic nanoparticles; and detecting the analyte-receptor complexes separated from the free receptors; characterized in that the step of separating the analyte-receptor complexes comprises the steps of: (a) putting a sample containing analytes and fluorescent-magnetic nanoparticles immobilized with the receptors into a tube attached with a selective filter, (b) making the fluorescent-magnetic nanoparticles attached to the wall of the tube at a state where a magnetic field is applied by a magnet that is placed on the outer portion of the tube, (c) applying a suction force to thus remove the remaining sample except for the fluorescent-magnetic nanoparticles attached to the tube wall from the tube, (d) putting a predetermined amount of a buffer solution into the tube at a state where the magnetic field by the magnet has been removed, (e) and applying the suction force from the outer portion of the selective filter that filters the fluorescent-magnetic nanoparticles that have been coupled with the analytes and passes the free fluorescent-magnetic nanoparticles that have not been coupled with the analytes, to then pass through the selective filter and to thereby remove the free fluorescent-magnetic nanoparticles that have not been coupled with the analytes. putting receptors into a sample containing the analytes to thus induce the receptors and the analytes to be coupled with each other, and to thereby form analyte-receptor complexes that are obtained by a coupling of the receptors with the analytes, respectively; separating the analyte-receptor complexes from free receptors that have not been coupled with the analytes; and wherein the receptors are used at a state being immobilized with fluorescent-magnetic nanoparticles; and detecting the analyte-receptor complexes separated from the free receptors; characterized in that the step of separating the analyte-receptor complexes comprises the steps of: (a) putting a sample containing analytes and fluorescent-magnetic nanoparticles immobilized with the receptors into a tube attached with a selective filter, (b) making the fluorescent-magnetic nanoparticles attached to the wall of the tube at a state where a magnetic field is applied by a magnet that is placed on the outer portion of the tube, (c) applying a suction force to thus remove the remaining sample except for the fluorescent-magnetic nanoparticles attached to the tube wall from the tube, (d) putting a predetermined amount of a buffer solution into the tube at a state where the magnetic field by the magnet has been removed, (e) and applying the suction force from the outer portion of the selective filter that filters the fluorescent-magnetic nanoparticles that have been coupled with the analytes and passes the free fluorescent-magnetic nanoparticles that have not been coupled with the analytes, (a) putting a sample containing analytes and fluorescent-magnetic nanoparticles immobilized with the receptors into a tube attached with a selective filter, (b) making the fluorescent-magnetic nanoparticles attached to the wall of the tube at a state where a magnetic field is applied by a magnet that is placed on the outer portion of the tube, (c) applying a suction force to thus remove the remaining sample except for the fluorescent-magnetic nanoparticles attached to the tube wall from the tube, (d) putting a predetermined amount of a buffer solution into the tube at a state where the magnetic field by the magnet has been removed, (e) and applying the suction force from the outer portion of the selective filter that filters the fluorescent-magnetic nanoparticles that have been coupled with the analytes and passes the free fluorescent-magnetic nanoparticles that have not been coupled with the analytes, to then pass through the selective filter and to thereby remove the free fluorescent-magnetic nanoparticles that have not been coupled with the analytes.