Prior to applying of ultraviolet rays to a surface of a wafer with a protective tape joined thereto that is placed and held on a holding table, an illumination sensor moves to a position below an ultraviolet irradiation unit having ultraviolet light emitting diodes arranged in one dimensional array to measure ultraviolet intensity in a position corresponding to a surface of the protective tape, and output voltage of each diode is controlled so as to maintain a uniform accumulated quantity of light in an area of the protective tape where ultraviolet rays are applied that is determined from the result of measurement and a turning velocity of the holding table.