PROBLEM TO BE SOLVED: To provide a low-cost LED lighting system used for a plant cultivation device using artificial light as a light source in a plant factory, vegetable factory or seedling raising device.SOLUTION: The LED lighting system 1 includes: a plate-shaped radiation member 2 an LED unit 3 attached to one side of the radiation member 2 and having a substrate 8, an LED chip 9 mounted in the substrate 8 and a reflector 11 disposed in such a way as to enclose the LED chip 9 a translucent plate 4 disposed on the side of the radiation member 2 on which the LED unit 3 is mounted with a space to the radiation member 2 and a spacer 5 disposed between peripheral edges of the radiation member 2 and the translucent plate 4 to fill the gap between the peripheral edges of the radiation member 2 and the translucent plate 4. The radiation member 2 is made of two layered aluminum heat conductive plates 6 and 7, and the mechanical strength of the outer heat conductive plate 7 is higher than the mechanical strength of the inner heat conductive plate 6 of the two heat conductive plates 6 and 7 constituting the radiation member 2. The LED unit 3 is mounted on the inner heat conductive plate 7 of the radiation member 2.
