A light source apparatus for supplying an endoscope with light includes at least one light source unit for generating the light. A transparent light homogenizer includes an entrance end face, disposed on a proximal side in an optical axis direction, for receiving entry of the light, an exit end face, disposed on a distal side in the optical axis direction, for exiting the light traveling from the entrance end face, and a reflective interface, formed in a tubular shape between the entrance end face and the exit end face, for total reflection of the light in an internal manner and for directing the light in the optical axis direction. A photo sensor is disposed on the reflective interface, for measuring a light amount of the light. The light homogenizer regularizes the light amount of the light from the exit end face in a radial direction.
