PURPOSE: To produce high purity silicon efficiently by measuring the temp. of the growing part of silicon and regulating the rate of feed of one or more among starting material for silicon, halogen and hydrogen according to the temp.

CONSTITUTION: When silicon is grown by a rotating and pulling method, the temp. of the lower end 19of a polycrystalline silicon body 8 is measured with a thermometer 20 such as infrared temp. sensor. The temp. signal is transmitted to regulators 12, 13, 14 for regulating the flow rates of starting material for silicon, hydrogen and halogen so as to control the opening and shutting of valves 15, 16, 17. By this control of the flow rates, the temp. of the lower end 19 of the silicon body 8 is regulated to 1,000°CW the m.p. of silicon, that is, 1,414°C. By this method, the rate of deposition of silicon is increased with low consumption of electric power and high purity silicon can be produced at a low cost.