To provide a liquid crystal display device that includes a cold cathode fluorescent lamp that controls a drop in the luminous efficacy of a fluorescent substance layer in a large electrical current region. Uneven portions UNE are formed in a surface of a fluorescent substance film FLU that is formed on an inner wall surface of a glass tube VAL that configures a cold cathode fluorescent lamp CCFL, whereby the surface area of the film surface can be increased and a drop in the fluorescent substance luminous efficacy in a large current region can be controlled, so the effect of improving the luminance of a display screen over a long period of time is obtained as a backlight of a liquid crystal display panel LCD.