A metallic glass fastening screw that is not susceptible to loosening, and is capable of implementing fastening with high strength and reliability. In processing a screw thread and a screw groove of a screw, amorphous bulk metallic glass is form-rolled at glass transition temperature or less of the bulk metallic glass serving as a member to be processed. The bulk metallic glass has a plastic strain property introduced by plastic working such as form rolling, to improve ductility. A relationship of d>0.022×D is set so that a depth from a bottom of the screw groove in the region where the plastic strain is introduced is d and an outside diameter of the screw is D, to relax stress concentration of tensile stress generated in a region at the bottom of the screw groove due to tension (axial force) applied to the screw in fastening.