The present invention relates to an edge-type lighting device using an LED light source which has high light-emitting efficiency regardless of thermal expansion of a light guide plate. An LED light source (3) is disposed on an edge of a light guide plate (2) so as to be movable in the normal line direction (±n) of the edge (2c) of the light guide plate. A slide member (7) is slidably disposed on the rear surface of the LED light source. A spring (8) is disposed in a frame member (4) on the rear surface of the slide member. Thus, the LED light source can always be pressed toward the edge of the light guide plate regardless of the thermal expansion of the light guide plate. Because the spring has a simple structure, the lighting device can be compact compared to the case where a coil spring is used.