A method of processing a workpiece includes a holding step, a height position detecting step, a modified layer forming step, and a dividing step. The height position detecting step is a step of, after the holding step, applying a measuring laser beam emitted from a height position detecting unit to the workpiece while moving a chuck table that holds the workpiece thereon and the height position detecting unit relatively to each other to detect a height position of the workpiece using a reflected beam from a reverse side of the workpiece. In the height position detecting step, the measuring laser beam is applied clear of areas of the workpiece where columnar conductive electrodes are embedded in streets.