An illuminating device is provided for use as a backlight of a liquid crystal display, and has a plurality of light sources and a light guiding plate emitting lights from the light sources outward. At least one of the light sources is configured to be lighted independently from the rest of the light sources. This illuminating device is applied to equipment such as a two surface display type cellular phone and is disposed between a main panel and a sub-panel to illuminate both panels. All light sources may be used to illuminate the main panel when the main panel is used, and some of the light sources may be used to illuminate only an area of the sub-panel when the sub-panel is used so that effective illumination may be implemented. Accordingly, light sources need not to be unnecessarily lighted when the sub-panel is used, which leads to low power consumption.