PURPOSE: To provide glass flux having low thermal expansion, having low yield point and low thermal expansion and capable of applying deep color to ceramic products.

CONSTITUTION: Glass raw materials are mixed so as to contain 1-10wt.% of Li2O, 5-35wt.% of Al2O3, 20-65wt.% of SiO2, 20-60wt.% of PbO and l-10wt.% of B2O3 and the mixture is melted, cooled and solidified and then, pulverized. The glass raw material contains preferably an solubilizing agent such as an alkali metal oxide or alkaline earth metal. The glass raw material contains preferably a crystallizing agent such as TiO2, ZrO2 or SnO2. A coloring raw material such as pigment or paint for ceramics is preferably added to the glass flux.