Brazing diamond particles to a steel substrate using Ni-based filler alloy was carried out via laser in an argon atmosphere. The brazed diamond particles were detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDS). The formation mechanism of carbide layers was discussed. All the results indicated that a high-strength bond between the diamond particles and the steel substrate was successfully realized. The chromium in the Ni-based alloy segregated preferentially to the surfaces of the diamonds to form a chromium-rich reaction product, and the bond between the alloy and the steel substrate was established through a crossdiffusion of iron and Ni-based alloy.