An edge-lit backlight unit and a display device are provided. The backlight unit includes a light guide plate and a rubber frame, wherein, the light guide plate includes a main body portion, the main body portion is of a flat plate structure and includes a first main surface, and a second main surface which are opposite to each other and a lateral surface, and the lateral surface includes a first lateral surface portion used as a light incident side and a second lateral surface portion outside the first lateral surface portion; the light guide plate further includes an extending portion extending outwards from at least a part of the second lateral surface portion of the main body portion, and a thickness of the extending portion is smaller than that of the main body portion.