Processing method

A cutting apparatus for cutting a chamfered outer peripheral portion of a workpiece, comprising:

• a chuck table having a holding surface that holds the workpiece;
• a processing unit that processes the workpiece held on the chuck table;
• a height measurement unit that measures heights of the workpiece held on the chuck table;
• and
• a controller that controls at least the chuck table, the processing unit, and the height measurement unit of the cutting apparatus, wherein
• the controller includes:
• a height distribution calculation section that calculates height distribution data of an outer periphery of the workpiece by measuring the heights of the workpiece at locations inside by a predetermined distance from an outer peripheral edge portion thereof with the height measurement unit while rotating the chuck table at least a full turn,
• a change rate calculation section that calculates height change rates as change rates of the heights of the outer periphery in the workpiece, based on the height distribution data calculated by the height distribution calculation section,
• a determination section that determines, based on results of comparison between the height change rates and a threshold, whether or not foreign matter exists on a back surface of the workpiece, and
• an error notification section that gives notification of an error if the foreign matter is determined to exist on the back surface of the workpiece.