To provide a backlight device capable of reducing luminance unevenness and color unevenness in the edge-light type backlight device capable of local dimming control.

The edge-light type backlight device has a plurality of light guide plates and a plurality of light sources corresponding to the plurality of light guide plates. Each of light sources includes one or more light-emitting elements and is arranged so that light may enter into an incident surface of each light guide plate, and the light guide plates have a reflection and diffusion surface to reflect and diffuse the light entering from the incident surface, an emitting surface from which the light diffused by the reflection and diffusion surface is emitted, and a light guide part which guides the light from the incident surface to the emitting surface. Out of the plurality of light guide plates, the light guide plates, which have longer distance of light reaching from the incident surface to the emitting surface of the light guide plate through the light guide part and the reflection and diffusion surface, are arranged nearer the liquid crystal display panel, and the light guide plates, which have shorter distance, have more number of the light-emitting elements included in the light sources corresponding to the light guide plates.