A first holding table suction-holds an annular projection of a wafer remaining on a rear face thereof for surrounding a back grinding region. A second holding table having an outer peripheral wall adjacent to an inner wall of the annular projection is inserted into a flat portion inside the annular projection for joining a separating adhesive tape to a protective tape on a surface of the wafer while a flat plane of the flat portion is suction-held. Thereafter, the adhesive tape is separated. Accordingly, the adhesive tape is separated from the surface of the wafer together with the protective tape.