A fluorescence light source device includes a wavelength conversion member that emits fluorescence by excitation laser light. The wavelength conversion member has an excitation laser light receiving surface including a periodic structure having a periodic array of conical or truncated projections with an aspect ratio, which is a ratio of the height of the projection to the pitch in the periodic structure, of not lower than 0.2. The wavelength conversion member is formed from a phosphor composed of a polycrystal and contains a micro-scatterer with a refractive index of not lower than 1.0 for scattering the excitation laser light and fluorescence emitted from the phosphor. A ratio (T/R) between a light transmission percentage T [%] in the wavelength conversion member and a light reflection percentage R [%] in the wavelength conversion member is 1 to 20.