The light source apparatus of the present disclosure includes a solid-state light source, a dichroic mirror for reflecting blue excitation light emitted from the solid-state light source, a phase difference plate for receiving the excitation light reflected on the dichroic mirror, a fluorescent plate having a fluorescent region irradiated with the excitation light, which is reflected on the dichroic mirror and transmitted through the phase difference plate, to emit fluorescent light and a reflection region for reflecting the excitation light, and a plurality of condenser lenses that are disposed between the phase difference plate and the fluorescent plate and condense the excitation light and the fluorescent light. Among the plurality of condenser lenses, the condenser lens closest to the fluorescent plate is made of a glass material having a linear expansion coefficient of 32.5×10−7 or less.