The present invention has as its object the provision of a fluorescence light source apparatus that is prevented from a drop in reflectance and can provide high emission efficiency over a long period of time without causing the problem of exfoliation of a reflection layer from a fluorescent plate. The fluorescence light source apparatus according to the present invention includes a fluorescent plate that is made of a phosphor for emitting fluorescence under excitation light and a metal oxide and has a front surface serving as an excitation light incident surface, a reflection layer disposed on a back surface side of the fluorescent layer, and a heat dissipation substrate. A sealing layer covering the back surface and a peripheral side surface of the reflection layer is provided in close contact with a peripheral area of the back surface of the fluorescent plate via an adhesion layer.