To provide a diamond bead which prevents the positional shift and the rotation with respect to a wire, and further to provide a wire saw which utilizes the diamond bead and has excellent durability.

The diamond wire saw 10 has a plurality of diamond beads 20 attached to a wire 12 at an appropriate interval. The diamond bead 20 has a diamond layer 26 on the outer circumferential surface of a nearly cylindrical core metal 22. The inner circumferential surface of the core metal 22 is provided with a screw portion 28 formed over the almost whole surface by a helicoidally continued groove portion 28A, and also a key way 30 having a nearly rectangular cross section is formed on the inner circumferential surface of the core metal 22 in the axial direction of the core metal 22 from the end portion 22A to the end portion 22B. When the wire 12 is inserted into the though-hole 24 of the diamond bead 20, and fixing material 32 is press-fit into the clearance, the axial positional shift of the wire 12 is suppressed by the fixing material 32 filled in the groove portion 28A, and further the circumferential rotation of the wire 12 is suppressed by the fixing material 32 which the key way 30 is filled with.