A reinforcing-plate fixed to a reinforced semiconductor wafer is separated from the wafer which includes a semiconductor wafer, a double-side adhesive sheet having, on at least one surface thereof, a peelable adhesive layer stuck to a front face of the semiconductor wafer, and the reinforcing-plate fixed to the other adhesive layer of the double-side adhesive sheet. A method includes separating the reinforcing-plate together with the double-side adhesive sheet from the reinforced semiconductor wafer by the peeling-effect of the peelable adhesive layer of the double-side adhesive sheet. The method further includes separating the reinforcing-plate from an arbitrarily selected edge of the semiconductor wafer toward an edge thereof different from the above-mentioned edge.