A driving method of a light source apparatus includes causing a primary light source to emit checking light. The checking light has light intensity sufficient to check a state of the light source apparatus and unharmful to the human body even when the checking light leaks. This emission is based on an output signal from a photodetector having detected a light radiated from a light conversion unit. The method further includes checking a state of the light source apparatus. The checking the state of the light source apparatus is based on an output signal from the photodetector having detected light radiated from the light conversion unit and entering the photodetector based on the checking light.