A useful method of modifying the surface of diamond powders with sulfur-containing functionalities was developed by the use of the photolysis of elemental sulfur. The sulfur-modified diamond powder exhibited a surface-attachment behavior to gold nanoparticles through the sulfur-containing linkage. In brief, the exposure of the modified diamond powders to gold colloids resulted in gold nanoparticles being attached to the diamond powders. The introduction of sulfur-containing functional groups and gold nanoparticles on the diamond surfaces was confirmed by means of XPS, DRIFT and mass spectroscopy analyses. Subsequently, the probe DNA attached onto the gold-modified diamond powder showed a DNA hybridization behavior by the treatment with a fluorescence-labeled target DNA oligonucleotide.