A LED module includes a printed circuit board, LEDs which are vertically mounted on the printed circuit board and which emit light onto a side surface, and a contact member which is provided to come into contact with a light guide plate. The printed circuit board may be movably coupled to a bottom chassis. When the light guide plate undergoes thermal expansion, the LED module may move by pressing of the light guide plate acting on the contact member. Accordingly, a gap between the light guide plate and the LEDs may be uniformly maintained even when the light guide plate undergoes thermal expansion or is returned to an original state.