Disclosed are a backlight unit and a display apparatus using the same. The backlight unit includes first and second reflectors, a light source module, an optical member spaced apart from the second reflector, a first cover to come into contact with the second reflector and optical member, a second cover coupled to the first cover to support the light source module, and a third cover coupled to the first and second covers. The first cover includes a bottom plate, first lateral plates facing each other with respect to a first direction, second lateral plates facing each other in a second direction, a first coupling portion disposed at each first lateral plate and coupled to the second cover, a second coupling portion disposed at each second lateral plate and coupled to the optical member, and a third coupling portion disposed at each second lateral plate and coupled to the third cover.