In center type cylindrical grinding, rotational error motion of workpieces is produced by geometrical errors of the center and center hole, their alignment error, lubricating condition in center holes, etc. In order to improve circularity of the ground workpiece, it is necessary to reduce the error motion. In practice, however, it is difficult to keep the geometrical conditions of the center and center hole ideal. The present paper describes a newly developed method for improving the circularity of ground workpieces in spite of the existence of the geometrical errors of the center and center hole. In this method, at the first stage, workpieces are ground by a conventional grinding method, then, the error motion and the circularity profile of ground surfaces are evaluated by using special in-situ measurement technique developed on the basis of the three-point method. At the next stage, the workpieces are reground, controlling the depth of cut minutely so as to remove convex parts of their circularity profile by elastically deflecting the center in the direction perpendicular to the wheel surface by means of a piezo-actuator.