A backlight unit includes a light source; a light guide plate; and an optical member on the light guide plate. The optical member includes first insulating patterns into which light from the light guide plate is incident to the optical member; a first insulating layer which covers the first insulating patterns; second insulating patterns into which light from the first insulating layer is incident; and a second insulating layer which covers the second insulating patterns. The light guide plate includes a light incident side surface, pairs of insulating patterns each include one first insulating pattern and one second insulating pattern, and in a top plan view, for each pair of insulating patterns, the first insulating pattern is closer to the light incident side surface than the second insulating pattern.