Provided is a polycrystalline silicon wafer produced by a melting and unidirectional solidification method, where the polycrystalline silicon wafer has a diameter of 450 mm or more, a thickness of 900 μm or more, and an average crystal grain size of 5 to 50 mm, and is made up of one piece. The present invention provides a large-sized polycrystalline silicon wafer having a wafer size of 450 mm or more, of which: mechanical properties are similar to those of monocrystalline silicon wafers; the crystal size is large; the surface roughness is low; the surface has a high cleanliness; the polished surface has less unevenness by having a definite crystal orientation; and the sag value is similar to that of monocrystalline silicon wafers.