A process for producing a single-crystal semiconductor and an apparatus therefor. A single-crystal semiconductor of large diameter and large weight can be lifted with the use of existing equipment not having any substantial change thereto while not influencing the oxygen concentration of single-crystal semiconductor and the temperature of melt and while not unduly raising the temperature of seed crystal. In particular, the relationship (L1, L2, L3) between the allowable temperature difference (.DELTA.T) and the diameter (D) of seed crystal (14) is preset so that the temperature difference between the seed crystal (14) at the time the seed crystal (14) is immersed in the melt and the melt (5) falls within the allowable temperature difference (.DELTA.T) at which dislocations are not introduced into the seed crystal (14). In accordance with the relationship (L1, L2, L3), the allowable temperature difference (.DELTA.T) corresponding to the diameter (D) of seed crystal (14) to be immersed in the melt is determined. Temperature control is conducted so that at the time the seed crystal (14) is immersed in the melt (5) the temperature difference between the seed crystal (14) and the melt (5) falls within the determined allowable temperature difference (.DELTA.T).