An LED module includes a single-sided circuit board, a plurality of LED strings and signal wires. The single-sided circuit board has a surface defined with a first and second areas. A long edge of the surface has a wiring outlet located at a position corresponding to a boundary of the first and second areas. The LED strings are divided into a first and second groups disposed in the first and second areas, respectively. The signal wires each are disposed on the surface and routed to have its one end joined to the wiring outlet, and its another end electrically connected to a first end of one LED string or a second end of one LED string. In addition, some signal wires each are further routed to have a segment thereof passed through a gap formed between the two groups of LED strings.