Method of processing workpiece

A method of processing a workpiece having a first region and a second region that are layered together to thin down the workpiece, comprising:

• acquiring a thickness of the first region;
• thinning down the second region by bringing a processing tool into contact with the workpiece held on a holding table;
• measuring and acquiring a thickness of the second region of the workpiece that has been thinned down;
• adjusting a positional relation between the processing tool and the holding table by referring to a total thickness of the workpiece that includes the acquired thickness of the first region and the acquired thickness of the second region;
• and
• thinning down the workpiece by bringing the processing tool into contact with the workpiece held on the holding table after the positional relation between the processing tool and the holding table has been adjusted.