To provide an LED light source device in which temperature increase of the surroundings is prevented while having a long life and being energy-saving.

The LED light source device supplies light to a light guide plate and is equipped with an LED unit 2, an installation board 3 on which the LED unit 2 is installed, an outer tube 4 installed so as to surround the LED unit 2, an inner tube 5 which supports a ball lens 8 to condense the light from the LED unit 2 to the front at the inside of a base part and in which the base part is housed in the outer tube 4, a casing 6 which houses the LED unit 2, the installation board 3, the outer tube 4, and the inner tube 5 inside, and a connecting part 7 which is screwed to a thread part formed at the tip of the inner tube 5 and pinches the wall of the casing 6 between the tip face of the inner tube 5, and to which the light guide 9 is connected.