The separation measurements of a bulk lifetime υo, front and back surface recombination velocities S0, Sw have been investigated for both 620 μm and 1.08 mm thick Si wafers with various surface treatments. The separation was made by applying bisurface photocoductivity decay method to the photoconductivity decay curves measured by 500 MHz microwave reflection under the bias light illumination. The bulk lifetime and the surface recombination velocities have been determined, respectively, to be 624–659 μs and 18.4–66.1 cm/s for the oxidized sliced-surface and 6285 cm/s for the sliced surface. And they have been also determined, respectively, to be 412–422 μs and <1 cm/s for the oxidized mirror polished-surface or the oxidized etched surface, 565–626 μs and 1042–1112 cm/s for the oxidized sandblasted-surface. The noncontact microwave BSPCD method with bias lights makes it possible to determine separately the bulk lifetime and surface recombination velocities in the front surface and backsurface in Si wafers with the wafer thickness for the practical use.