Disclosed is an SPFS sensor chip by which an antigen-antibody reaction or fluorescence can be detected at the maximum efficiency. The SPFS sensor chip, which comprises a transparent substrate, a metal film, an SAM, a solid phase layer having a three-dimensional structure and a ligand, is characterized in that, in said sensor chip, the fluctuation rate represented by the following formula is 0-30% inclusive: [half-width (α)-half width (ss)]/half width (ss)100 [wherein half-width (α) is obtained from a graph that its drawn by plotting the intensity of reflected light of light entering at a definite angle from one surface of sold transparent substrate, said surface not being in contact with the metal film and said reflected light intensity being measured with a light intensity detector placed on the opposite surface side of the transparent substrate, against the angle; and half width (ss) represents the half width of the sensor chip comprising the transparent substrate and the metal film].