A backlight module includes two light guide plates, two light-emitting modules, and a controller. Each of the light guide plates has an incident surface and a light-output surface. The light guide plates are arranged side-by-side to make the light-output surfaces be coplanar. Each of the light-emitting modules is configured to provide a first kind of light and a second kind of light to the incident surface of the corresponding light guide plate. The first kind of light has a first triplet. The second kind of light has a second triplet different from the first triplet. The controller is configured to asynchronously drive any of the light-emitting modules to alternately provide the first kind of light and the second kind of light.