There is provided a sensing chip capable of measuring a refractive index by utilizing a long-range surface plasmon polariton, accurately measuring an accumulative refractive index in a wide range, and more easily enabling sealing for measurement. The present invention relates to the sensing chip which has a thin metal film or a strip-like metal grown on an underlayer, and has a dielectric that limits a refractive index and a dielectric buffer layer on an upper surface and a lower surface of the thin metal film or the strip-like metal. The dielectric buffer layer is attached onto the thin metal film or the strip-like metal. The thin metal film or the strip-like metal and the buffer layer are sandwiched between two dielectric layers. A hole is made in a surface of the upper dielectric layer to serve as a measurement groove.