An LED back-light unit and other devices using the LED back-light unit are discussed. According to one embodiment, an LED back-light unit includes a light guide portion that includes a light guide plate and a reflection plate coupled to the light guide plate, wherein the light guide plate has a light input part and a first connection part, and wherein the reflection plate has a second connection part connected to the first connection part, and a light source including at least one light emitting diode, the light source emitting light toward the light guide portion.