To provide a centerless grinding machine which can quickly and easily carry out the adjustment for retooling according to the variation of the diameter of workpieces by improving the centerless grinding machine.

A regulating wheel head 7 is mounted on a flat type bed 14 via a horizontal slide mechanism 15, and supports a regulating wheel 2. A grinding wheel head 6 is fixed on the flat type bed, and supports a grinding wheel 3 in the Z-axis direction. The center R of the regulating wheel 2 is arranged at the position lower than the center G of the grinding wheel 3 by (h), and is slid in the horizontal direction. When the diameter of a workpiece 5 becomes large, the regulating wheel 2 is horizontally slid rightward in the figure. When the diameter of a workpiece 5 becomes small, the regulating wheel 2 is horizontally slid leftward in the figure. By such adjustment, the centerless grinding machine can cope with the workpieces having various diameters without changing a center height.