PURPOSE: To obtain a decorative glass excellent in design characteristic and suitable for louver for illumination use by subjecting glass blocks, having shape of cube or rectangular parallelepiped, to mutual welding and precipitating crystals only in the vicinity of the interface between mutual glass interface.

CONSTITUTION: Glass blocks having shape of cube or rectangular parallelepiped (soda-lime glass blocks in which the length of one edge is regulated to 5-50mm is preferred) are laid one on top of the other so that respective surfaces are allowed to adhere to each other and these glass blocks are held at 780-1000°C for 1-12hr, by which respective glass blocks are welded together and crystals are precipitated only in the vicinity of the glass interface (preferred thickness of crystalline layer is 20-2000μm). By this method, the decorative glass can be obtained.