To rapidly grind a semiconductor bar without damaging the semiconductor bar itself and a grinding machine by providing a turning head having a plunge grinding wheel, a cup grinding wheel, and a measuring device for measuring the diameter and the length of a work.

This grinding machine is provided with a turning head 1 in which a plunge grinding wheel 2, a cup grinding wheel 3, and a measuring device 7 are arranged. By rotating the turning head 1 around the axis, either of the plunge grinding wheel 2 or the cup grinding wheel 3 grinds a semiconductor bar 6 sandwiched between a work driving device 4 and a tail-stock 5. The measuring device 7 is extended for measuring the length of the bar 6, and compares the length value already input by an operator with the measured length value in a computer. When this value is different by a fixed tolerance for example about 5 mm, the program is interrupted so as not to damage the grinding machine or the semiconductor bar 6 itself.