A method for processing a workpiece in which a tool smaller than the workpiece is caused to scan the workpiece includes the steps of dwelling a tool on a dummy work for a predetermined time to process the dummy work, measuring the dummy work to determine a unit removal shape, causing the tool to scan the dummy work, and processing the dummy work while continuously changing a dwell time of the tool so that the dwell time is a linear function with respect to a scanning position of the tool. Additional processing steps include measuring a change of a depth or volume of a removal shape processed in the dummy work, to thereby determine a removal rate corresponding to a continuous change of the dwell time of the tool, determining a tentative dwell time to dwell the tool at respective processed points from a target removal shape of the workpiece and the unit removal shape, determining the removal rate corresponding to the tentative dwell time at the respective processed points, and determining a true dwell time at the respective processed points from the removal rate at the respective processed points. The tool dwells for the true dwell time at the respective processed points to process the workpiece.