During relative and horizontal movement of a mount frame, in which a semiconductor wafer with a protective tape is supported on a ring frame through a supporting adhesive tape, and a joining member, a position of an end edge of the protective tape is detected in a non-contact manner. Based on the detection result, a joining member is stopped in the position of the end edge of the protective tape and is moved close to the semiconductor wafer to press and bring a separation tape against and into contact with an end of the protective tape. In this state, the mount frame and the joining member are relatively and horizontally moved to join the separation tape onto the protective tape. Then, the mount frame and the joining member are relatively and horizontally moved to separate the separation tape together with the protective tape from a surface of the semiconductor wafer.