A backlight module includes a light source, a light guide plate and a light-adjusting member. A light source chromaticity is measured from light generated by the light source. The light guide plate has a light-incident surface and a light-emitting surface. Light generated by the light source enters the light guide plate and emits out from the light-emitting surface. With the light-adjusting member, a first light guide plate chromaticity is measured from the light-emitting surface. There is a first difference value between the first light guide plate chromaticity and the light source chromaticity. Without the light-adjusting member, a second light guide plate chromaticity is measured from the light-emitting surface. There is a second difference value between the second light guide plate chromaticity and the light source chromaticity. The first difference value is different from the second difference value.