A backlight unit 12 includes LED units 17, a light guide plate 18 and a follow-up mechanism. The light guide plate 18 has light entrance surfaces 18b and a light exit surface 18a. The light entrance surfaces 18b are provided so as to face the respective LED units 17. The light exit surface 18a is provided parallel to an arrangement direction in which the LED units 17 and the light entrance surface 18b are arranged (i.e., the Y-axis direction) and such that light exits therethrough. The follow-up mechanism is configured to move the LED unit 17U in the arrangement direction in response to a deformation of the light guide plate 18. The follow-up mechanism includes a support member 20 that supports the LED unit 17U. The support member is in contact with a surface of the light guide plate 18 along the light entrance surface 18bU.