A method of processing a workpiece with a cutting blade, the workpiece having a body of metal disposed in superposed relation to projected dicing lines, including: a first metal burr removing step of moving the cutting blade through first cut grooves while the cutting blade is positioned at such a height that a lowermost end of the cutting blade is lower than an upper end of the body of metal; and a second metal burr removing step of moving the cutting blade through the second cut grooves while the cutting blade is positioned at such a height that the lowermost end of the cutting blade is lower than the upper end of the body of metal. A liquid containing an organic acid and an oxidizing agent is supplied to the workpiece in the first metal burr removing step and the second metal burr removing step.