Truing method and apparatus

In a truing method and apparatus, an analyzing method is employed to calculate a truing shape from which a grinding surface having been trued with a grinding wheel (9) being rotated at a low rotational speed during a truing operation is deformed to a desired shape due to centrifugal expansion depending on a rotational speed difference when the grinding wheel (9) is rotated at a high rotational speed during a grinding operation. Then, with the grinding wheel (9) being rotated at the low rotational speed, the grinding surface is trued with a truing roll (11) to the calculated truing shape. As a result, the grinding surface of the grinding wheel (9) being rotated at the low rotational speed is trued with the truing roll (11) taking into consideration the centrifugal expansion of the grinding surface which takes place when the grinding wheel (9) is rotatated at the high rotational speed during the grinding operation subsequent to the truing operation.