A backlight unit includes side emitting-type LEDs, a light guide plate, and an LED board. The light guide plate includes a light entering end surface, a light exiting plate surface, and an opposite plate surface. The LED board includes a plate surface attached to an edge of the opposite plate surface. A gap in a range from 0.1 mm to 0.2 mm is provided between light emitting surfaces of the LEDs and the light entering end surface. The edge of each light emitting surface is at a position ΔD1 mm inner than an edge of the light entering end surface with respect to a thickness direction of the light guide plate. An edge of each light emitting surface is at a position ΔD2 mm inner than an edge of the light entering end surface. ΔD1 and ΔD2 satisfy relational expressions: ΔD2≥ΔD1 and ΔD2≥0.1.