NOVELTY - A rotational cooling shaft of crystal sheet apparatus has concave portions formed between convex portions (2) on its periphery. Crystal or semiconductor material is precipitated on the concave-convex surface. By immersing convex portion into the hot fusion liquid of semiconductor material.    USE - For manufacturing crystal sheet e.g. polycrystalline silicon wafer of big crystal grains, for solar batteries.    ADVANTAGE - The silicon wafer is formed by a process not based on crystal slicing process. Silicon sheet of desired thickness is obtained by altering the immersion depth of convex portion of shaft, appropriately. The adhesion strength of the cooling rotational shaft and silicon sheet is reduced relatively, by making the width of the concave portion more than width of convex portion, and the silicon sheet is easily peeled from the shaft. As the width of the concave portion is wider, bigger crystal grains are formed. The cooling shaft has improved strength. The convex portion is reliably immersed to hot fused silicon liquid and silicon sheet of moderate thickness is formed. The crystal sheet is peelable continuously from the corrugated structure easily. The surface of the convex portion can be prevented from damage. Continuous operation is possible. Temperature is controlled accurately and nucleus growth in the convex portion can be accelerated.    DETAILED DESCRIPTION - The width of the convex portion is narrower than the width of the concave portion. The width of convex portion is 5 mm or more and the depth of the concave portion is 5 mm or more.    An INDEPENDENT CLAIM is also included for crystal sheet manufacturing apparatus which comprises a cooling shaft with concave and convex portions. A gas introduction pipe (4) blows off cooling gas through a nozzle (5) to cool convex portion (2) immersed in hot fusion liquid of semiconductor material.    DESCRIPTION OF DRAWING(S) - The figure shows the sectional drawing of cooling rotational shaft. (Drawing includes non-English language text).    Convex portion (2)    Concave portion (3)    Gas introduction portion (4)    Nozzle (5)