A light source apparatus includes a main unit, light source modules attachable to and detachable from the main unit, and storage mediums storing characteristic information of the light source modules. Each light source module includes at least one light source and a light connection part to be optically connected to the main unit. The main unit includes entrance parts to be optically connected to the light connection parts of the connected light source modules, a light combining unit to combine light entering the entrance parts, at least one exit part to cause light combined by the light combining unit to exit, and an exit light characteristic deriving unit to derive characteristic information of achievable exit light based on characteristic information of the light source modules stored in the storage mediums.
