Disclosed is a backlight unit and LCD device having a fixing device attached to a bottom cover and a guide panel to prevent the guide panel from shifting and detaching from the bottom cover. The backlight unit comprises a bottom cover having a bottom portion including a first hole, and a side portion having a second hole; a light guide plate on the bottom portion of the bottom cover; at least one optical sheet on the light guide plate; a guide panel adjacent the guide plate and the optical sheet; and a fixing device. The fixing device includes a horizontal portion; and a side portion extending perpendicularly from the horizontal portion. The side portion includes second protrusion portions extending inward from an edge of the side portion and parallel to the horizontal portion, and supporting portions extending vertically from the side portion at distal ends of the side portion.