PURPOSE: To produce optical glass wherein ununiformity such as a stria is easily eliminated by heating glass ununiform in optical properties in the atmosphere of high-pressure gas.

CONSTITUTION: High-silica glass having ≥95% silica content or quartz glass is heated at ≥1,800°C preferably at 2,200W2,400°C in the high-pressure atmosphere of ≥2 atm preferably 5W25 atm. Still further any one of argon, nitrogen and helium or its gaseous mixture is used as the high-pressure atmosphere and a graphite heater is used as a heating source. Thereby ununiformity such as a stria for glass can easily be eliminated and excellent optical glass is obtained.