A back light unit includes a light guide plate having a rectangle shape with first and second edges and a light source having a light element to emit light to a first edge of the light guide plate. The light guide plate emits the incident light from the light source to a liquid crystal display panel as a flat light source. An elastic frame is integrally formed with first and second frame elements in a rectangle shape so as to surround the light guide plate. The light source includes a metal frame clipped by a clip shape implemented provided in the first frame element. The first edge facing the second edge of the light guide plate is fitted to the metal frame. The second edge of the light guide plate is fitted to a second frame element having a clip portion for clipping the light guide plate.