There is provided a forming mold made on the basis of a standard more reliable than an average roughness of a surface of a metal film that generates surface plasmon resonance, the forming mold being capable of improving an S/N ratio of an optical element. A forming mold 40 includes a fixed mold 41 and a movable mold 42. A molding surface 51t is provided at a tip end of a core section 51 of the fixed mold 41. When an Spc value of the molding surface 51t is equal to or less than 100 (1/mm), the state of a surface 21a of a substrate 21, on a side facing an object to be measured, obtained by transferring the molding surface 51t can be made smooth to the extent that the generation of a scattering light in a metal film 22 to be formed on this surface 21a can be appropriately suppressed. Thus, it is possible to improve an S/N ratio in the measurement using Surface Plasmon-field enhanced Fluorescence Spectroscopy. In contrast, when the Spc value of the molding surface 51t is equal to or greater than 30 (1/mm), the mo
