Abstract: A backing pad for supporting semiconductor wafer allowing an advanced flatness of its mirror-polished surface even for large sized wafers. A backing pad 1 is smoothly finished on its wafer holding surface 1a, thereon a number of grooves 2, 2 . . . aligned in a lattice form and elongated toward the outer periphery of the backing pad 1. The backing pad is typically made of polyurethane poromerics internally including a number of isolated pores. All of the grooves 2 are equal in the width and depth, which are kept constant along their lengthy direction. Intergroove pitch is also kept constant over the entire wafer holding surface 1a. The backing pad 1 is enlarged in its diameter to allow simultaneous loading of a plurality of wafers W, W . . . .