A light source apparatus is adapted to be shared by excimer lamps. An IC tag is disposed at each lamp, and the IC tag stores information identifying the lamp. A storage unit of the light source apparatus stores information identifying a usable lamp (or usable lamps) for the light source apparatus, an emission wavelength of the lamp, and a sensitivity correction value of an optical sensor that corresponds to the emission wavelength. When the light source apparatus is driven to cause the lamp to light, the information stored in the IC tag and information stored in the storage unit are collated and it is determined whether the lamp is usable and the emission wavelength of the lamp is a preset emission wavelength. If it is determined that the lamp is usable and the emission wavelength is appropriate, the sensitivity of the optical sensor is corrected with the correction value.