Disclosed is a backlight unit and a display device using the same, which includes a first reflector, a second reflector 300 and at least one light source module 100 disposed between the first and second reflectors, wherein a back surface of the first reflector comprises an inclined plane 201 and a flat surface 202, with facing the second reflector, and the inclined plane is adjacent to the light source and the flat surface is extended from an end of the inclined plane, with the inclined plane and the flat surface being collinear.