A method for preparing a silicon epitaxial wafer that includes a silicon single crystal wafer sliced from a CZ silicon ingot doped with carbon in a concentration range of not less than 5×1015 atoms/cm3 and not more than 5×1017 atoms/cm3 and an epitaxial layer consisting of a silicon single crystal epitaxially grown on a front surface of the silicon single crystal wafer. A polycrystalline silicon layer having a thickness of not less than 0.5 μm and not more than 1.5 μm is formed on a back surface of the silicon single crystal wafer.