Abstract: An improved apparatus for growing a single crystal of semiconductor silicon by the Czochralski method which apparatus has a heat-resistant and heat-insulating covering board in direct contact with the upper ends of heat-insulating members surrounding a quartz glass silicon melting crucible and having a circular center opening, and a heat-resistant and heat-insulating tube having an outer diameter approximately equal to the diameter of the center opening in the covering board gas-tightly joined to an upwardly extending argon gas supplying conduit and extending downwardly from the joint of the top wall of a metal housing and the upwardly extending conduit and extending through the center opening in the covering board in such a manner that the single crystal during growing is coaxially surrounded thereby, the lower end thereof being at a height above and in the proximity of the surface of the melt in the crucible.