GRINDING DEVICE

PROBLEM TO BE SOLVED: To reduce erroneous operation of a device due to an incorrect detection value of the thickness of a workpiece.SOLUTION: The thickness detection device 7 includes: a detection part for detecting the thickness of a semiconductor wafer W; a storage part 73 for storing the thickness detection value of the detection part; a regulation part 74 for regulating the storage of the storage part 73 of the thickness detection values at and less than the lower limit value that allows the storage part 73 to store the thickness detection value; and a control unit 75 for continuing grinding with a grinding unit 6 by lowering the lower limit value by the predetermined amount when the gap between the thickness detection value stored in the storage part 73 and the lower limit value becomes less than the predetermined value, and stopping grinding by the grinding unit 6 when the thickness detection value stored in the storage part 73 becomes the desired value or less.