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.