Abstract: The present invention provides a process for preparing SOI wafer, more specifically, a process for preparing a large-sized SOI wafer of high quality of crystallization employing an apparatus for the manufacture of the SOI wafer in a simple and efficient manner. The apparatus for the manufacture of SOI wafer of the invention comprises electric furnace for heating polycrystalline silicon filled in a heat-resistant container; means for moving up and down of an insulating substrate whose one side is accompanied with silicon single crystalline seed, and immersing the substrate in the molten silicon filled in the heat-resistant container to form a thin single crystalline film on the substrate; and, shapers to keep a constant thickness of the thin single crystalline film which is formed on the insulating substrate by the moving means.