PURPOSE: To obtain the appropriate shape of cross sectional edge face by providing the computer analyzing the measured value from measuring part wherein the piezo-electric elements opposite to the cross sectional edge face of ingot-side are arranged and the controller for a dressing device.

CONSTITUTION: A measuring part 2 is composed of the measuring pieces wherein piezo-electric elements are arranged, and they are pushed against the cross sectional edge faces of ingots 1, whereby their deformations are detected precisely. A computer 5 analyzes the measured values and controls a dressing device 6, and then regulates the shape of a cutting blade 3. Then first, a standard value is set, and the edge faces of nth and (n+1)th ingots are measured, and then said measured values are analyzed. If the measured value of (n+1)th edge face is deviated from the allowance of flatness, a machine is stopped and is again regulated. Next, the difference of the displacement between (n+1)th edge face and nth edge face is calculated, and the calculated value is compared with the set value. If the calculated value is different from the set value, the dressing of the cutting blade 3 or its cutting speed is regulated, and the machine is regulated so that the calculated value approaches to the set value, and then cutting is achieved. If the calculated value is similar to the set value, the cutting is continued until the cutting number reaches a prescribed number, while the measurement is repeated.