Disclosed is a processing method which can achieve a high processing rate, and is capable of making a surface smooth. In order to achieve this an SiC substrate is arranged in a potassium hydroxide solution containing hydrogen peroxide, and ultraviolent radiation is irradiated on the surface of the SiC substrate. An SiO2 layer is formed on the surface of the SiC substrate due to the irradiation of ultraviolet radiation, and this SiO2 layer is chemically removed by means of the potassium hydroxide solution, and also removed by a synthetic quartz surface plate.