A light source module includes a light guide element, at least one light-emitting element, and a quantum dot element. The light guide element has a light incident surface and a light exiting surface. The light-emitting element is disposed at the light incident surface for providing a first color light. The quantum dot element converts only a portion of the first color light into a first monochromatic light. The first color light and the first monochromatic light are mixed into a white light.