A structural material of diamond like carbon (DLC) composite layers is provided. The structural material includes a composite material which is consisted of a metal layer, a first metal nitride layer, and a DLC thin film. The metal layer includes aluminum (Al), copper (Cu), zirconium (Zr), nickel (Ni), or vanadium (V). The first metal nitride layer includes aluminum nitride (Al—N), zirconium nitride (Zr—N), vanadium nitride (V—N), or nickel nitride (Ni—N). The DLC thin film of the structural material of DLC composite layers has high quality tetragonally bonded amorphous carbon (ta-C) with a sp3(C—C) bonding ratio of more than 30%. Therefore, it is suitable for the work pieces in the mechanical, chemical, electricity, photoelectric, and heat transfer fields.