A method of manufacturing a semiconductor wafer of the present invention includes the steps of: obtaining a composite base by forming a base surface flattening layer having a surface RMS roughness of not more than 1.0 nm on a base; obtaining a composite substrate by attaching a semiconductor crystal layer to a side of the composite base where the base surface flattening layer is located; growing at least one semiconductor layer on the semiconductor crystal layer of the composite substrate; and obtaining the semiconductor wafer including the semiconductor crystal layer and the semiconductor layer by removing the base surface flattening layer by wet etching and thereby separating the semiconductor crystal layer from the base. Thus, a method of manufacturing a semiconductor wafer capable of efficiently manufacturing the semiconductor wafer regardless of the type of a base, and a composite base and a composite substrate suitably used in that manufacturing method are provided to efficiently manufacture a semiconductor device.