A LED illuminating device includes an illuminating unit and a shell having a top side and chamber. The illuminating unit includes a PCB supported by the shell and one or more LED modules electrically and spacedly mounted on the PCB disposed in the chamber. Each of the LED modules includes a red LED, a blue LED and a green LED which are symmetrically arranged in a triangular manner side by side. The wires are emerged from two ends of the shell in a horizontal plane parallel to an adhesive layer so as to adapt for electrically linking two neighboring LED modules with each other in a flat plane manner. Finally, it reduces unnecessary length of the wire and minimizes the size of the device by decreasing the overall volume.