Provided is a sintered silicon wafer in which the maximum crystal grain size is 20μm or less and the average crystal grain size is 1μm or more but not more than 10μm; specifically, provides is a sintered silicon wafer having the following mechanical properties measured by collecting a plurality of test samples from the sintered silicon wafer having a diameter of 400mm or more, namely, the average deflecting strength based on a three-point bending test of 20kgf/mm2 or more but not more than 50kgf/mm2, the average tensile strength of 5kgf/mm2 or more but not more than 20kgf/mm2, and the average Vickers hardness of Hv 800 or more but not more than Hv 1200. The provided sintered silicon wafer is a sintered compact wafer having a fixed strength and mechanical properties similar to those of single-crystal silicon even when it is a sintered silicon wafer of large-size disk shape.