To provide a smooth cut surface and the correct perpendicularity of the cut surface without damaging the machinability by main beads.

This diamond wire saw comprises a metallic stranded wire 6; main beads 7 fixed to the wire 6 with the prescribed intervals; and spacers 11 which are formed around the wire 6 between the main beads 7, protect the wire 6, and prevent the movement of the main beads 7. The main bead 7 comprises a cylindrical pedestal 8 fixed around the wire 6, and a cutting abrasive grain layer 9 formed around the pedestal 8. At least one cylindrical auxiliary bead 10 with the outside diameter same as that of the main bead 7 and having the cut surface grinding function and the wire vibration preventing function is provided at the position away from an end part of the main bead 7 by the length L1 of the main bead 7 so as to satisfy the inequality of L1+L2+ L3...+Ln≤2L1, where L1, L2, L3...Ln are the length of the auxiliary beads 10.