Abstract: The present invention provides a method for identifying a glass defect source, whereby a glass defect source can directly be identified without using a mathematical simulation. The method for identifying a glass defect source, which comprises a step of constructing a glass melting furnace by using, as lining furnace material, a fusion cast refractory containing at least one tracer component selected from Cs2O, SrO, BaO and ZnO, a step of melting a glass material by the glass melting furnace and forming the molten glass material to produce glass products, and a step of extracting one having a glass defect from the glass products and analyzing its component composition to determine the position of a glass defect source in the glass melting furnace.