A light source apparatus for fluorescence photography of biomolecule sample gels is disclosed. The light source apparatus comprises a housing, a transparent plate disposed in a light transmission zone at the top of the housing, and at least one LED array disposed in the housing out of the range of the light transmission zone. The LED array irradiates obliquely to the light transmission zone for preventing the light spots from interfering in the observation. Each of LED array may comprises different colors of LEDs for different biomolecule samples.