A backlight unit for a liquid crystal display device, including: a bottom cover comprising a bottom surface and at least one side surface extending from the bottom surface of the bottom cover at an angle greater than 0° and smaller than 180° with respect to the bottom surface; a plurality of light sources disposed on the bottom surface; and a support side arranged on the bottom surface at the side surface of the bottom cover, the support side being configured to reflect light and to change a path of light from the plurality of light sources, the support side including a plurality of support side members oriented at different angles relative to the bottom surface of the bottom cover, wherein the support side comprises: a first support side member having a first end disposed on the bottom surface of the bottom cover; and a second support side member having a first end connected to a second end of the first support side member, the second support side member having a surface slanted at a first angle (α) relative to the bottom surface of the bottom cover, and characterized in that the difference (b) between the height of the first support side member evaluated in a direction perpendicular to the bottom surface of the bottom cover and the lower illumination height of light from the plurality of light sources is greater than or equal to 0mm and less than or equal to 3mm, the lower illumination height being defined as: X*tanβ, where β denotes a light orientation angle being the minimum angle of light emitted by the light sources with respect to the bottom cover, and where X denotes the distance between the first support side member to the center of the light source of the plurality of light sources being closest to the first support side member. a bottom cover comprising a bottom surface and at least one side surface extending from the bottom surface of the bottom cover at an angle greater than 0° and smaller than 180° with respect to the bottom surface; a plurality of light sources disposed on the bottom surface; and a support side arranged on the bottom surface at the side surface of the bottom cover, the support side being configured to reflect light and to change a path of light from the plurality of light sources, the support side including a plurality of support side members oriented at different angles relative to the bottom surface of the bottom cover, wherein the support side comprises: a first support side member having a first end disposed on the bottom surface of the bottom cover; and a second support side member having a first end connected to a second end of the first support side member, the second support side member having a surface slanted at a first angle (α) relative to the bottom surface of the bottom cover, and characterized in that the difference (b) between the height of the first support side member evaluated in a direction perpendicular to the bottom surface of the bottom cover and the lower illumination height of light from the plurality of light sources is greater than or equal to 0mm and less than or equal to 3mm, the lower illumination height being defined as: X*tanβ, where β denotes a light orientation angle being the minimum angle of light emitted by the light sources with respect to the bottom cover, and where X denotes the distance between the first support side member to the center of the light source of the plurality of light sources being closest to the first support side member. a first support side member having a first end disposed on the bottom surface of the bottom cover; and a second support side member having a first end connected to a second end of the first support side member, the second support side member having a surface slanted at a first angle (α) relative to the bottom surface of the bottom cover, and characterized in that the difference (b) between the height of the first support side member evaluated in a direction perpendicular to the bottom surface of the bottom cover and the lower illumination height of light from the plurality of light sources is greater than or equal to 0mm and less than or equal to 3mm, the lower illumination height being defined as: X*tanβ, where β denotes a light orientation angle being the minimum angle of light emitted by the light sources with respect to the bottom cover, and where X denotes the distance between the first support side member to the center of the light source of the plurality of light sources being closest to the first support side member.