The present invention provides an LED (Light Emitting Diode) illumination unit, an LED illumination device, and an LED illumination system with better visual effect. The LED illumination unit includes: a substrate, having a carrying surface with an x direction as a length direction and a y direction as a width direction and facing a z direction; a plurality of LED chips, supported by the carrying surface of the substrate; a casing, allowing the light emitted from the LED chips to penetrate and covering the LED chips; and a heat dissipation component, having a pair of outside surfaces being planar, and mounted with the substrate and the casing, wherein the pair of outside surfaces is configured opposite and parallel to each other in the y direction at an interval, and is longer than the substrate in the x direction.