Fluorescence light source device with wavelength conversion member with particular ratio between light transmission percentage and light reflection percentage

A fluorescence light source device comprising a wavelength conversion member for emitting fluorescence by excitation laser light, wherein

• the wavelength conversion member has an excitation light receiving surface including a periodic structure having a two-dimensional periodic array of conical or truncated projections,
• the wavelength conversion member has a fluorescence member formed from a phosphor composed of a polycrystal, the fluorescence member has a thickness of 0.05 to 0.2 mm and contains a micro-scatterer formed from an inorganic compound particle with a refractive index of not lower than 1.0 for scattering the excitation laser light and fluorescence emitted from the phosphor, and the micro-scatterer has a diameter of 500 to 8000 nm, and
• the wavelength conversion member has 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 within a range of 1 to 20.