A high-quality polycrystalline bulk semiconductor having a large crystal grain size is produced by the casting method in which growth is regulated so as to proceed in the same plane direction, i.e., the {110}; plane or {112} plane is disclosed. The process, which is for producing a polycrystalline bulk semiconductor, comprises: a step in which a melt of a semiconductor selected among Si, Ge, and SiGe is held in a crucible; a step in which a bottom part of the crucible is cooled to give a temperature gradient and that part of the melt which is located directly on the crucible bottom is rapidly cooled in the beginning of growth to supercool the melt around the crucible bottom; a step in which the crucible is cooled to grow nuclei on the crucible bottom due to the supercooled state of the melt around the crucible bottom and thereby grow dendritic crystals along the crucible bottom; and a step in which a polycrystalline bulk of the semiconductor is then grown on the upper side of the dendritic crystals.