A light source apparatus capable of adapting to multiple types of observation light for intended purposes is provided. The light source apparatus 10 includes a main unit 40, light source modules 20A, 20B, and 20C attachable to and detachable from the main unit 40, and storage mediums 24A, 24B, and 24C storing characteristic information of the light source modules 20A, 20B, and 20C. The light source modules each include at least one light source 21A, 21B, and 21C and a light connection part 23A, 23B, and 23C to be optically connected to the main unit 40. The main unit includes: entrance parts 41A, 41B, and 41C to be optically connected to light connection parts 23A, 23B, and 23C； a light combining unit 43 to combine light entering the entrance parts 41A, 41B, and 41C； an exit part 45 to cause the combined light to exit； and an exit light characteristic deriving unit 48 to derive characteristic information of achievable exit light.
