To provide an acceptable building glass block using cathode-ray tube panel glass cullet as a raw material, and to provide a method for manufacturing the glass block.

A hollow building glass block is obtained by integrally combining a pair of open bottomed glass molded bodies in a state where their open end edges are in contact with each other, wherein the glass block is made of an SiO₂-Al₂O₃-RO-R'₂O (R is an alkaline earth metal and R' is an alkali metal) glass containing, by mass%, 0.1-5% of Al₂O₃ and 10-36% of SrO+BaO and satisfying, on a mass basis, (SrO+BaO)/ΣRO=0.6-1.0.