A workpiece is fixed by a retracting mechanical chuck mounted on a spindle head of a five-axis control machining center. The apparent outer diameter of the workpiece is increased by a jig. Clamp surfaces of the jaws and a support surface of the jig are formed on the machining center. A cutting tool is mounted on a spindle by an automatic tool exchanger. The workpiece is rotated about an axis to grind an end surface of the workpiece to approximately a predetermined target shape, which is a spherical surface. A grinder is then mounted on the spindle by the automatic tool exchanger, and the grinder is set relative to the workpiece by five-axis control such that the inclination angle, the offset amount, etc. satisfy a predetermined relationship according to the desired grinding. The grinder is then fed in the Z-axis direction to form the spherical surface by grinding.