of the lens l this angle of rotation is detected by the encoder 333 and the control section 100 manages the processing configuration in accordance with the detected angle of rotation this makes it possible to eliminate the axial offset and perform the high accuracy processing even if the suction cup 50 is somewhat deformed and or an excessively large chuck pressure is not applied in the event that a large angular deviation not smaller than a predetermined angular deviation is found between the rotation of the drive shaft i e the left chuck shaft 302 l driven by the pulse motor 342 and the rotation of the driven shaft i e the right chuck shaft 302 r detected by the encoder 333 a determination is made such that a large load is applied to the lens l on the basis of which the motor 370 for moving the carriage 300 is controlled to lower the processing pressure and avoid the application of the large load alternatively the large load applied to the lens l may be removed by stopping the rotative driving of the motor 342 or slightly reversing the motor 342 this makes it possible to continuously apply an optimum processing load to the lens without changing the chuck pressure depending on the difference in lens material accordingly processing.