An SPFS (Surface Plasmon-field enhanced Fluorescence Spectroscopy) measurement method, comprising - providing a sensor chip for SPFS measurement which has a dielectric member constituting a prism, said dielectric member having been produced by carrying out injection molding of a resin, wherein a gate mark is set on one side end surface of the dielectric member , said one side end surface intersecting with an excitation light incoming surface of said dielectric member , a metal thin film-formed surface of said dielectric member , and a reflected light outgoing surface through which a reflected light that comes in through said excitation light incoming surface and is reflected by the metal thin film-formed surface of said dielectric member goes out, is used, when viewing from the metal thin film-formed surface side of said dielectric member and taking as b the distance of the side end surface position of said gate mark to the position on said metal thin film-formed surface that is farthest from the side end surface position of said gate mark , - positioning and fixing the sensor chip in an SPFS measurement device with which detection is carried out using positioning and fixing parts of the sensor chip , said positioning and fixing parts being formed in said dielectric member , and wherein one of said positioning and fixing parts is the gate mark ; - irradiating an excitation light to at least a portion of a metal thin film from the side where said dielectric member exists, said metal thin film having been formed on said dielectric member , said portion being located in the area between the 3b/8 position and the 6b/8 position from the side end surface position of said gate mark and - measuring fluorescence that is emitted by a fluorescent substance labeling an analyte immobilized by a ligand on said metal thin film to calculate the amount of the analyte. - providing a sensor chip for SPFS measurement which has a dielectric member constituting a prism, said dielectric member having been produced by carrying out injection molding of a resin, wherein a gate mark is set on one side end surface of the dielectric member , said one side end surface intersecting with an excitation light incoming surface of said dielectric member , a metal thin film-formed surface of said dielectric member , and a reflected light outgoing surface through which a reflected light that comes in through said excitation light incoming surface and is reflected by the metal thin film-formed surface of said dielectric member goes out, is used, when viewing from the metal thin film-formed surface side of said dielectric member and taking as b the distance of the side end surface position of said gate mark to the position on said metal thin film-formed surface that is farthest from the side end surface position of said gate mark , - positioning and fixing the sensor chip in an SPFS measurement device with which detection is carried out using positioning and fixing parts of the sensor chip , said positioning and fixing parts being formed in said dielectric member , and wherein one of said positioning and fixing parts is the gate mark ; - irradiating an excitation light to at least a portion of a metal thin film from the side where said dielectric member exists, said metal thin film having been formed on said dielectric member , said portion being located in the area between the 3b/8 position and the 6b/8 position from the side end surface position of said gate mark and - measuring fluorescence that is emitted by a fluorescent substance labeling an analyte immobilized by a ligand on said metal thin film to calculate the amount of the analyte. <EOS>