A backlight module with a detachable light source unit includes a light guide plate and a light source unit housed in a module case. The light source unit can slide along a lengthwise direction of one end face of the light guide plate. The light source unit is equipped with a U-shaped cover member for holding a plurality of point light sources such as LEDs along a lengthwise direction. The backlight module further includes a coupling member to change a positional relationship between the light guide plate and the light source unit such that a distance between an emitting surface of the LED and an incident plane of the light guide plate during a process of exchanging the light source unit is larger than that between the emitting surface and the incident plane at a time of home position of the light source unit in the module case.