The invention concerns a device for enhancing fluorescence comprising a support (10) carrying fluorescence enhancement means (11), the fluorescence enhancement means offering a reception surface for chemical or biological elements intended to be read by detection of a fluorescence signal emitted by a fluorophore, associated with the chemical or biological elements, under the effect of an excitation light beam. The fluorescence enhancement means (11) is made up of a thin, transparent, dielectric layer or a stack of thin, transparent, dielectric layers (12 to 16) ensuring a mirror function for the fluorescence signal and excitation light beam, the material of the thin layer or of each thin layer of the stack being chosen from among the following materials: TiO.sub.2, Ta.sub.2O.sub.5, HfO.sub.2, ZrO.sub.2, MgO, SiO.sub.2, Si.sub.3N.sub.4, MgF.sub.2 and YF.sub.3. The fluorescence enhancement device may be used for a biological or chemical optic sensor.