A light source apparatus including a light-emitting module and a control unit is provided. The light-emitting module is configured to provide a light. The control unit is configured to make the light switched between a first light and a second light so that at least one of a blue-light hazard and a circadian stimulus value of the light is changed. A wavelength of a blue light main peak in a spectrum of the first light is different from a wavelength of a blue light main peak in a spectrum of the second light.